NATIONAL GEOGRAPHIC MAGAZINE.

Vol. I. 1888. No. 1.

INTRODUCTORY ADDRESS.

BY THE PRESIDENT, MR. GARDINER G. HUBBARD.

I am not a scientific man, nor can I lay claim to any special knowledge that would entitle me to be called a "Geographer." I owe the honor of my election as President of the National Geographic Society simply to the fact that I am one of those who desire to further the prosecution of geographic research. I possess only the same general interest in the subject of geography that should be felt by every educated man.

By my election you notify the public that the membership of our Society will not be confined to professional geographers, but will include that large number who, like myself, desire to promote special researches by others, and to diffuse the knowledge so gained, among men, so that we may all know more of the world upon which we live.

By the establishment of this Society we hope to bring together (1) the scattered workers of our country, and (2) the persons who desire to promote their researches. In union there is strength, and through the medium of a national organization, we may hope to promote geographic research in a manner that could not be accomplished by scattered individuals, or by local societies; we may also hope—through the same agency—to diffuse the results of geographic research over a wider area than would otherwise be possible.

The position to which I have been called has compelled me to become a student. Since my election I have been trying to learn the meaning of the word "geography," and something of the history of the science to which it relates. The Greek origin of the word ([Greek: gê], the earth, and [Greek: graphê], description) betrays the source from which we derived the science, and shows that it relates to a description of the earth. But the "earth" known to the Greeks was a very different thing from the earth with which we are acquainted.

To the ancient Greek it meant land—not all land, but only a limited territory, in the centre of which he lived. His earth comprised simply the Persian Empire, Italy, Egypt and the borders of the Black and Mediterranean seas, besides his own country. Beyond these limits, the land extended indefinitely to an unknown distance—till it reached the borders of the great ocean which completely surrounded it.

To the members of this society the word "earth" suggests a very different idea. The term arouses in our minds the conception of an enormous globe suspended in empty space, one side in shadow and the other bathed in the rays of the sun. The outer surface of this globe consists of a uniform, unbroken ocean of air, enclosing another more solid surface (composed partly of land and partly of water), which teems with countless forms of animal and vegetable life. This is the earth of which geography gives us a description.

To the ancients the earth was a flat plain, solid and immovable, and surrounded by water, out of which the sun rose in the east and into which it set in the west. To them "Geography" meant simply a description of the lands with which they were acquainted.

Herodotus, who lived about the year 450 B.C., transmitted to posterity an account of the world as it was known in his day. We look upon him as the father of geography as well as of history. He visited the known regions of the earth, and described accurately what he saw, thus laying the foundations of comparative geography.

About 300 years B.C., Alexander the Great penetrated into hitherto unknown regions, conquered India and Russia, and founded the Macedonian Empire. He sent a naval expedition to explore the coasts of India, accompanied by philosophers or learned men, who described the new countries discovered and the character of their inhabitants. This voyage may be considered as originating the science of Political Geography, or the geography of man.

About the year 200 B.C., Eratosthenes of Cyrene, the keeper of the Royal Library at Alexandria, became convinced, from experiments, that the idea of the rotundity of the earth, which had been advanced by some of his predecessors, was correct, and attempted to determine upon correct principles its magnitude. The town of Cyrene, on the river Nile, was situated exactly under the tropic, for he knew that on the day of the summer solstice, the sun's rays illuminated at noon the bottom of a deep well in that city. At Alexandria, however, on the day of the summer solstice, Eratosthenes observed that the vertical finger of a sun-dial cast a shadow at noon, showing that the sun was not there exactly overhead. From the length of the shadow he ascertained the sun's distance from the zenith to be 7° 12', or one-fiftieth part of the circumference of the heavens; from which he calculated that if the world was round the distance between Alexandria and Cyrene should be one-fiftieth part of the circumference of the world. The distance between these cities was 5000 stadia, from which he calculated that the circumference of the world was fifty times this amount, or 250,000 stadia. Unfortunately we are ignorant of the exact length of a stadium, so we have no means of testing the accuracy of his deduction. He was the founder of Mathematical Geography; it became possible through the labors of Eratosthenes to determine the location of places on the surface of the earth by means of lines corresponding to our lines of latitude and longitude.

Claudius Ptolemy, in the second century of the Christian era, made a catalogue of the positions of plans as determined by Eratosthenes and his successors, and with this as his basis, he made a series of twenty-six maps, thus exhibiting, at a glance, in geographical form, the results of the labors of all who preceded him. To him we owe the art of map-making, the origination of Geographic Art.

We thus see that when Rome began to rule the world, the Greeks had made great progress in geography. They already possessed Comparative, Political and Mathematical Geography, and Geographic Art, or the art of making maps.

Then came a pause in the progress of geography.

The Romans were so constantly occupied with the practical affairs of life, that they paid little attention to any other kind of geography than that which facilitated the administration of their empire. They were great road-builders, and laid out highways from Rome to the farthest limits of their possessions. Maps of their military roads were made, but little else. These exhibited with accuracy the less and greater stations on the route from Rome to India, and from Rome to the further end of Britain.

Then came the decline and fall of Rome, and with it the complete collapse of geographical knowledge. In the dark ages, geography practically ceased to exist. In the typical map of the middle ages, Jerusalem lay in the centre with Paradise on the East and Europe on the West. It was not until the close of the dark ages that the spirit of discovery was re-awakened. Then the adventurous Northmen from Norway and Sweden crossed the ocean to Iceland.

From Iceland they proceeded to Greenland and even visited the main-land of North America about the year 1000 A.D., coasting as far south as New England; but these voyages led to no practical results, and were forgotten or looked upon as myths, until within a few years. For hundreds of years geography made but little advance—and the discoveries of five centuries were less than those now made in five years. In the fourteenth or fifteenth century, the mariner's compass was introduced into Europe from China, and it then became possible to venture upon the ocean far out of sight of land. Columbus instead of coasting from shore to shore like the ancient Northmen, boldly set sail across the Atlantic. To many of his contemporaries it must have seemed madness to seek the East by thus sailing towards the West, and we need hardly wonder at the opposition experienced from his crew. The rotundity of the earth had become to him an objective reality, and in sublime faith he pursued his westward way. Expecting to find the East Indies he found America instead. Five centuries had elapsed since the Northmen had made their voyages to these shores—and their labors had proved to be barren of results. The discovery of Columbus, however, immediately bore fruit. It was his genius and perseverance alone that gave the new world to the people of Europe, and he is therefore rightfully entitled to be called the discoverer of America. His discovery was fraught with enormous consequences, and it inaugurated a new era for geographic research. The spirit of discovery was quickened and geographic knowledge advanced with a great leap. America was explored; Africa was circumnavigated. Magellan demonstrated the rotundity of the earth by sailing westward until he reached his starting point. Everywhere—all over the civilized world—the spirit of adventure was aroused. Navigators from England, Holland, France and Spain rapidly extended the boundaries of geographical knowledge, while explorers penetrated into the interior of the new lands discovered. The mighty impetus given by Columbus set the whole world in motion and it has gone on moving ever since with accelerated velocity.

The great progress that has been made can hardly be realized without comparing the famous Borgia map, constructed about one hundred years before the discovery of America, with the modern maps of the same countries; or Hubbard's map of New England made two hundred years ago, with the corresponding map of to-day. The improvements in map-making originated with Mercator, who, in 1556 constructed his cylindrical projection of the sphere. But it has been only during the last hundred years that great progress has been made. Much yet remains to be done before geographic art can fully accomplish its mission.

The present century forms a new era in the progress of geography—the era of organized research. In 1830, the Royal Geographical Society of England was founded, and it already forms a landmark in the history of discovery. The Paris Society preceded it in point of time, and the other countries of Europe soon followed the example. Through these organizations, students and explorers have been encouraged and assisted, and information systematically collected and arranged. The wide diffusion of geographical knowledge through the medium of these societies and the publicity of the discussions and criticism that followed, operated to direct the current of exploration into the most useful channels. Before organized effort, darkness gave way at every step. Each observer added fresh knowledge to the existing store, without unnecessary duplication of research. The reports of discoveries were discussed and criticized by the societies, and the contributions of all were co-ordinated into one great whole.

America refuses to be left in the rear. Already her explorers are in every land and on every sea. Already she has contributed her quota of martyrs in the frozen north, and has led the way into the torrid regions of Africa. The people of Europe, through Columbus, opened up a new world for us; and we, through Stanley, have discovered a new world in the old, for them.

Much has been done on land—little on the other three-quarters of the earth's surface. But here America has laid the foundations of a new science,—the Geography of the Sea.

Our explorers have mapped out the surface of the ocean and discovered the great movements of the waters. They have traced the southward flow of the Arctic waters to temper the climate of the torrid zone. They have followed the northward set of the heated waters of the equator and have shown how they form those wonderful rivers of warm water that flow, without walls, through the colder waters of the sea, till they strike the western shores of Europe and America, and how they render habitable the almost Arctic countries of Great Britain and Alaska. They have even followed these warm currents further and shown how they penetrate the Arctic Ocean to lessen the rigors of the Arctic cold. Bravely, but vainly, have they sought for that ignis fatuus of explorers—the open polar sea—produced by the action of the warm waters from the south.

American explorers have sounded the depths of the ocean and discovered mountains and valleys beneath the waves. They have found the great plateaus on which the cables rest that bring us into instantaneous communication with the rest of the world. They have shown the probable existence of a vast submarine range of mountains, extending nearly the whole length of the Pacific Ocean—mountains so high that their summits rise above the surface to form islands and archipelagoes in the Pacific. And all this vast region of the earth, which, a few years ago, was considered uninhabitable on account of the great pressure, they have discovered to be teeming with life. From the depths of the ocean they have brought living things, whose lives were spent under conditions of such pressure that the elastic force of their own bodies burst them open before they could be brought to the surface; living creatures whose self-luminous spots supplied them with the light denied them in the deep abyss from which they sprang—abysses so deep that the powerful rays of the sun could only feebly penetrate to illuminate or warm.

The exploring vessels of our Fish Commission have discovered in the deep sea, in one single season, more forms of life than were found by the Challenger Expedition in a three years' cruise. Through their agency, we have studied the geographical distribution of marine life; and in our marine laboratories, explorers have studied the life history of the most useful forms.

The knowledge gained has enabled us to breed and multiply at will; to protect the young fish during the period of their infancy—when alone they are liable to wholesale destruction—finally to release them in the ocean, in those waters that are most suitable to their growth. The fecundity of fish is so great, and the protection afforded them during the critical period of their life so ample, that it may now be possible to feed the world from the ocean and set the laws of Matthews at defiance. Our geographers of the sea have shown that an acre of water may be made to produce more food for the support of man than ten acres of arable land. They have thrown open to cultivation a territory of the earth constituting three-quarters of the entire surface of the globe.

And what shall we say of our conquests in that other vast territory of the earth, greater in extent than all the oceans and the lands put together—the atmosphere that surrounds it.

Here again America has led the way, and laid the foundations of a Geography of the Air. But a little while ago and we might have truly said with the ancients "the wind bloweth where it listeth, and we know neither from whence it comes nor whither it goes"; but now our explorers track the wind from point to point and telegraph warnings in advance of the storm.

In this department, the Geography of the Air, we have far outstripped the nations of the world. We have passed the mob-period of research when the observations of multitudes of individuals amounted to little, from lack of concentrated action. Organization has been effected. A Central Bureau has been established in Washington, and an army of trained observers has been dispersed over the surface of the globe, who all observe the condition of the atmosphere according to a pre-concerted plan.

The vessels of our navy and the mercantile marine of our own and other countries have been impressed into the service, and thus our geographers of the air are stationed in every land and traverse the waters of every sea. Every day, at the same moment of absolute time, they observe and note the condition of the atmosphere at the part of the earth where they happen to be, and the latitude and longitude of their position. The collocation of these observations gives us a series of what may be termed instantaneous photographs of the condition of the whole atmosphere. The co-ordination of the observations, and their geographical representation upon a map, is undertaken by a staff of trained experts in the Central Bureau in Washington, and through this organization we obtain a weather-map of the world for every day of the year. We can now study at leisure the past movements of the atmosphere, and from these observations we shall surely discover the grand laws that control aerial phenomena. We shall then not only know, as we do at present, whence comes the wind and whither it goes, but be able to predict its movements for the benefit of humanity.

Already we have attained a useful, though limited, power of prediction.

Our Central Bureau daily collects observations by telegraph from all parts of this continent, and our experts are thus enabled to forecast the probabilities by a few hours. Day by day the results are communicated to the public by telegraph in time to avert disaster to the mariners on our eastern coast, and facilitate agricultural operations in the Eastern and Middle States.

Although many of the predictions are still falsified by events, the percentage of fulfilments has become so large as to show that continued research will in the future give us fresh forms of prediction and increase the usefulness of this branch of science to mankind.

In all departments of geographical knowledge, Americans are at work. They have pushed themselves into the front rank and they demand the best efforts of their countrymen to encourage and support.

When we embark on the great ocean of discovery, the horizon of the unknown advances with us and surrounds us wherever we go. The more we know, the greater we find is our ignorance. Because we know so little we have formed this society for the increase and diffusion of Geographical knowledge. Because our subject is so large we have organized the society into four broad sections: relating to the geography of the land, H. G. Ogden, vice-president; the sea, J. R. Bartlett, vice-president; the air, A. W. Greely, vice-president; the geographic distribution of life, C. H. Merriam, vice-president; to which we have added a fifth, relating to the abstract science of geographic art, including the art of map-making etc., A. H. Thompson, vice-president; our recording and corresponding secretaries are Henry Gannett and George Kennan.

We have been fortunate indeed to secure as Vice-Presidents men learned in each department, and who have been personally identified with the work of research.

GEOGRAPHIC METHODS IN GEOLOGIC INVESTIGATION.

BY W. M. DAVIS.

OUTLINE.

Definition of Geography and Geology—Geographic Methods in Geology—Hutton and Lyell—Marine deposits explained by existing processes reveal the history of the earth—American Topographers—First Pennsylvania Survey; geographic form as the result of extinct processes—Western Surveys; geographic form explained by existing processes reveals the history of the earth—Deductive Topography—Comparison with Palæontology—Geographic Individuals—Classification according to structure—Ideal cycle of regular development—Interruptions in the Simple Ideal Cycle—Geography needs ideal types and technical terms—Comparison with the biological sciences—Teaching of Geography—The water-falls of Northeastern Pennsylvania as examples of deductive study—Systematic Geography.

The history of the earth includes among many things an account of its structure and form at successive times, of the processes by which changes in its structure and form have been produced, and of the causes of these processes. Geography is according to ordinary definition allowed of all this only an account of the present form of the earth, while geology takes all the rest, and it is too generally the case that even the present form of the earth is insufficiently examined by geographers. Geographic morphology, or topography, is not yet developed into a science. Some writers seem to think it a division of geology, while geologists are as a rule too much occupied with other matters to give it the attention it deserves. It is not worth while to embarrass one's study by too much definition of its subdivisions, but it is clearly advisable in this case to take such steps as shall hasten a critical and minute examination of the form of the earth's surface by geographers, and to this end it may serve a useful purpose to enlarge the limited definition of geography, as given above, and insist that it shall include not only a descriptive and statistical account of the present surface of the earth, but also a systematic classification of the features of the earth's surface, viewed as the results of certain processes, acting for various periods, at different ages, on divers structures. As Mackinder of Oxford has recently expressed it, geography is the study of the present in the light of the past. When thus conceived it forms a fitting complement to geology, which, as defined by the same author, is the study of the past in the light of the present. The studies are inseparable and up to a certain point, their physical aspects may be well followed together, under such a name as physiography. Specialization may then lead the student more to one subject than to the other.

An illustration from human history, where the study of the past and present has a single name, may serve to make my meaning clear in regard to the relation of the two parts of terrestrial history, which have different names. A descriptive and statistical account of a people as at present existing, such as that which our statistical atlas of the last Census gives in outline, corresponds to geography in its ordinary limitation. A reasonable extension of such an account, introducing a consideration of antecedent conditions and events, for the purpose of throwing light on existing relations, represents an expanded conception of geography. The minute study of the rise and present condition of any single industry would correspond to the monographic account of the development of any simple group of geographic forms. On the other hand, history taken in its more general aspects, including an inquiry into the causes and processes of the rise and fall of ancient nations, answers to geology; and an account of some brief past stage of history is the equivalent of paleography, a subject at present very little studied and seemingly destined always to escape sharp determination. It is manifest that geology and geography thus defined are parts of a single great subject, and must not be considered independently.

History became a science when it outgrew mere narration and searched for the causes of the facts narrated; when it ceased to accept old narratives as absolute records and judged them by criteria derived from our knowledge of human nature as we see it at present, but modified to accord with past conditions.

Geology became a science when it adopted geographic methods. The interpretation of the past by means of a study of the present proves to be the only safe method of geologic investigation. Hutton and Lyell may be named as the prominent leaders of this school and if we admit a reasonable modification of their too pronounced uniformitarianism, all modern geologists are their followers. The discovery of the conservation and correlation of energy gives additional support to their thesis by ruling out the gratuitous assumption of great results from vague causes. Causes must be shown to be not only appropriate in quality, but sufficient in quantity before they can be safely accepted. But the geographic argument as expounded by the English school deals almost entirely with processes and neglects a large class of results that follow from these processes. Much attention is given to the methods of transferring the waste of the land to the sea and depositing it there in stratified masses, from which the history of ancient lands is determined. But the forms assumed by the wasting land have not been sufficiently examined. It was recognized in a general way that land forms were the product of denudation, but the enormous volume of material that had been washed off of the lands was hardly appreciated, and the great significance of the forms developed during the destruction of the land was not perceived.

Hutton says a little about the relation of topography to structure; Lyell says less. The systematic study of topography is largely American. There is opportunity for it in this country that is not easily found in Europe. The advance in this study has been made in two distinct steps: first, in the East about 1840; second, in the West about 1870. The first step was taken in that historic decade when our early State surveys accomplished their great work. The Pennsylvania surveyors then developed topography into a science, as Lesley tells us so eloquently in his rare little book "Coal and its Topography," 1856, which deserves to be brought more to the attention of the younger geographers and geologists of to-day. It presents in brief and picturesque form the topographical results of the first geological survey of Pennsylvania. It shows how Lesley and the other members of that survey "became not mineralogists, not miners, not learned in fossils, not geologists in the full sense of the word, but topographers, and topography became a science and was returned to Europe and presented to geology as an American invention. The passion with which we studied it is inconceivable, the details into which it leads us were infinite. Every township was a new monograph." (p. 125.) Some of the finest groups of canoes and zigzags developed on the folded beds of the Pennsylvania Appalachians are illustrated from studies made by Henderson, Whelpley and McKinley, and they certainly deserve the most attentive examination. I often feel that they have been of the greatest assistance in my own field work, especially in the efforts I have made to discover the structural arrangement of the Triassic lava sheets in the Connecticut valley. But although the intricacies of Appalachian topography were then clearly seen to depend on the complications of Appalachian structure, the process of topographic development was not at that time discovered. "The only question open to discussion is," says Lesley, "whether this planing down of the crust to its present surface was a secular or an instantaneous work" (p. 132), and he decides in favor of the latter alternative. He adds, that to the field worker, "The rush of an ocean over a continent ... leads off the whole procession of his facts, and is indispensable to the exercise of his sagacity at every turn" (p. 166). "The present waters are the powerless modern representatives of those ancient floods which did the work" (p. 151).

It is not the least in any spirit of disparagement that I quote these cataclysmic views, now abandoned even by their author. Great generalizations are not often completed at a single step, and it is enough that every effort at advance should have part of its movement in the right direction. What I wish to show is that topographic form was regarded in the days of our eastern surveys, even by our first master of American topography, as a completed product of extinct processes. Topography revealed structure, but it did not then reveal the long history that the structure has passed through. The anticlinal valleys, hemmed in by the even-topped sandstone mountains of middle Pennsylvania, were found to tell plainly enough that a vast erosion had taken place, and that the resulting forms depended on the structure of the eroded mass, but it was tacitly understood that the land stood at its present altitude during the erosion. The even crest lines of the mountains and the general highland level of the dissected plateau farther west did not then reveal that the land had stood lower than at present during a great part of the erosion, and thus the full lesson of the topography was not learned. The systematic relation of form to structure, base level and time; the change of drainage areas by contest of headwaters at divides; the revival of exhausted rivers by massive elevations of their drainage areas: all these consequences of slow adjustments were then unperceived. In later years there seems to be a general awakening to the great value of these principles, which mark the second stage in the advance of scientific topography, referred to above.

It is not easy to sketch the history of this awakening. Ramsay years ago contributed an element in his explanation of plains of marine denudation; Jukes opened the way to an understanding of cross valleys; Newberry excluded fractures from the production of the most fracture-like of all water ways; and our government surveyors in the western territories have fully developed the all important idea of base level, of which only a brief and imperfect statement had previously been current. I cannot say how far European geographers and geologists would be willing to place the highest value on the last named element; to me it takes the place of Lesley's ocean flood, in leading off the whole procession of outdoor facts. It is indispensable at every turn. Recently, mention should be made of Löwl, of Prague, who has done so much to explain the development of rivers, and of McGee, who has explicitly shown that we must "read geologic history in erosion as well as in deposition."

If it be true that the greater part of this second advance is American like the first, it must be ascribed to the natural opportunities allowed us. The topographers of the Appalachians had a field in which one great lesson was repeated over and over again and forced on their attention. The patchwork structure of Europe gave no such wide opportunity. The surveyors of the western territories again found broad regions telling one story, and all so plainly written that he must run far ahead who reads it. It is to this opportunity of rapid discovery and interpretation that Archibald Geikie alludes in the preface to the recent second edition of his charming volume on the "Scenery of Scotland." He says that since the book first appeared he has seen many parts of Europe, "but above all it has been my good fortune to have been able to extend the research into western America, and to have learned more during my months of sojourn there than during the same number of years in the Old Country." (p. vii.)

Our position now is, therefore, while structure determines form as our earlier topographers taught, and while form-producing processes are slow, as had been demonstrated by the English geologists, that the sequence of forms assumed by a given structure during its long life of waste is determinate, and that the early or young forms are recognizably different from the mature forms and the old forms. A young plain is smooth. The same region at a latter date will be roughened by the channeling of its larger streams and by the increase in number of side branches, until it comes to "maturity," that is to the greatest variety or differentiation of form. At a still later date the widening of the valleys consumes the intervening hills, and the form becomes tamer, until in "old age" it returns to the simple plain surface of "youth." Young mountains possess structural lakes and are drained largely by longitudinal valleys; old mountains have no such lakes and have transverse drainage, formed as the growing headwaters of external streams lead out much water that formerly followed the longitudinal valleys. Young rivers may have falls on tilted beds, but such are short lived. Falls on horizontal beds are common and survive on the headwater branches of even mature rivers. All falls disappear in old rivers, provided they are not resuscitated by some accident in the normal, simple cycle of river life. The phases of growth are as distinct as in organic forms. As this idea has grown in my mind from reading the authors above named, geography has gained a new interest. The different parts of the world are brought into natural relations with one another; the interest that change, growth and life had before given to the biologic sciences only, now extends to the study of inorganic forms. It matters not that geographic growth is destructive; it involves a systematic change of form from the early youth to the distant old age of a given structure, and that is enough. It matters not that the change is too slow for us to see its progress in any single structure. We do not believe that an oak grows from an acorn from seeing the full growth accomplished while waiting for the evidence of the fact, but because partly by analogy with plants of quicker development, partly by the sight of oaks of different ages, we are convinced of a change that we seldom wait to see. It is the same with geographic forms. We find evidence of the wasting of great mountains in the wasting of little mounds of sand; and we may by searching find examples of young, mature and old mountains, that follow as well marked a sequence as that formed by small, full grown and decaying oaks. If the relative positions of the members in the sequence is not manifest at first, we have the mental pleasure of searching for their true arrangement. The face of nature thus becomes alive and full of expression, and the conception of its change becomes so real that one almost expects to see the change in successive visits to one place.

Now consider the deductive application of this principle. Having recognized the sequence of forms developed during the wasting life of a single structure, reverse the conception and we have a powerful geographic method for geologic investigation. On entering a new country, apply there the principles learned from the inductive study of familiar regions, and much past history is revealed; the age of mountains may be deduced from their form as well as from their rocks; the altitudes at which a district has stood may be determined by traces of its old base levels, of which we learn nothing from the ordinary routine of geologic observation, that is, from a study of the structure and age of the rocks themselves. The principle is commonly employed nowadays, but its methods are not formulated, and its full value is hardly yet perceived. Heim has found traces of successive elevations in the Alps, proved by incipient base levels at several consistent altitudes on the valley slopes. Newberry, Powell and Dutton have worked out the history of the plateau and cañon region from its topography; Chamberlin and Salisbury write of the young and old topographic forms of the drift-covered and the driftless areas in Wisconsin; LeConte and Stephenson have interpreted chapters in the history of California and Pennsylvania from the form of the valleys. Recently McGee has added most interesting chapters to the history of our middle Atlantic slope, in an essay that gives admirable practical exposition of the geographic methods. In the light of these original and suggestive studies one may contend that when geographic forms in their vast variety are thus systematically interpreted as the surface features of as many structures, belonging to a moderate number of families and having expression characteristic of their age and accidents, their elevation and opportunity, then geography will be for the wasting lands what palæontology has come to be for the growing ocean floors.

An interesting comparison may be drawn here. Fossils were first gathered and described as individual specimens, with no comprehension of their relationships and their significance. It was later found that the fossils in a certain small part of the world, England—that wonderful epitome of geologic history—were arranged in sequences in the bedded rocks containing them, certain groups of forms together, successive groups in shelves, as it were, one over another. Then it was discovered that the local English scale had a wider application, and finally it has come to be accepted as a standard, with certain modifications, for the whole world. The exploring geologist does not now wait to learn if a formation containing trilobites underlies another containing ammonites, but on finding the fossils in the two, confidently and as far as we know correctly concludes that such is their relative position. Thus the sequence of submarine processes is made out by the sequence of organic forms. In brief, palæontology has passed largely from the inductive to the deductive stage.

The geographer first regarded the features of the land as completed entities, with whose origin he was in no wise concerned. Later it was found that some conception of their origin was important in appreciating their present form, but they were still regarded as the product of past, extinct processes. This view has been in turn displaced by one that considers the features of the land as the present stage of a long cycle of systematically changing forms, sculptured by processes still in operation. Now recognizing the sequence of changing forms, we may determine the place that any given feature occupies in the entire sequence through which it must pass in its whole cycle of development. And then reversing this conception we are just beginning to deduce the past history of a district by the degree of development of its features. Geography is, in other words, entering a deductive stage, like that already reached by palæontology.

The antecedent of deductive topography is the systematic study of land geography. The surface of the land is made up of many more or less distinct geographic individuals, every individual consisting of a single structure, containing many parts or features whose expression varies as the processes of land sculpture carry the whole through its long cycle of life. There is endless variety among the thousands of structures that compose the land, but after recognizing a few large structural families, the remaining differences may be regarded as individual. In a given family, the individuals present great differences of expression with age, as between the vigorous relief of the young Himalaya and the subdued forms of the old Appalachians; or with elevation over base level, as between the gentle plain of the low Atlantic coast and the precocious high plateaus of the Colorado river region; or with opportunity, as between the last named plateaus with exterior drainage and the high plains of the Great Basin, whose waters have no escape save by evaporation or high level overflow; or with complexity of history, as between the immature, undeveloped valleys of the lava block country of southern Oregon, and the once empty, then gravel-filled, and now deeply terraced inner valleys of the Himalaya. When thus studied, the endless variety of the topography will be considered in its proper relations, and it will not seem as hopeless as it does now to gain a rational understanding and appreciation of geographic morphology.

We should first recognize the fact that a geographic individual is an area, large or small, whose surface form depends on a single structure. Boundaries may be vague, different individuals may be blended or even superposed, but in spite of the indefiniteness, the attempt to sub-divide a region into the individuals that compose it will be found very profitable. In a large way the Appalachian plateau is an individual; the Adirondacks, the terminal moraine of the second glacial epoch are others. In a small way, a drumlin, a fan delta, a mesa, are individuals. The linear plateaus of middle Pennsylvania are hybrids between the well-developed linear ridges of the mountains farther east and the irregular plateau masses farther west.

A rough classification of geographic individuals would group them under such headings as plains, plateaus, and rough broken countries of horizontal structure; mountains of broken, tilted or folded structure, generally having a distinct linear extension; volcanoes, including all the parts from the bottom of the stem or neck, up to the lateral subterranean expansions known as laccolites, and to the surface cones and flows; glacial drift; wind drift. The agents which accomplished the work of denudation are also susceptible of classification: rivers according to the arrangement of their branches, and their imperfections in the form of lakes and glaciers. The valleys that rivers determine may be considered as the converse of the lands in which they are cut; and the waste of the land on the way to the sea is susceptible of careful discrimination: local soil, talus, alluvial deposits, fan cones and fan deltas, flood plains and shore deltas. Their variations dependent on climatic conditions are of especial importance. The structures formed along shore lines are also significant. This list is intentionally brief, and the lines between its divisions are not sharply drawn. It undoubtedly requires discussion and criticism before adoption. It differs but slightly from the common geographic stock in trade, but for its proper application it requires that the geographer should be in some degree a geologist.

The changes in any geographic individual from the time when it was offered to the destructive forces to the end of its life, when it is worn down to a featureless base level surface, are worthy of the most attentive study. The immaturity of the broken country of southern Oregon, as compared with the more advanced forms of the Basin ranges, is a case in hand. The Triassic formation of the Connecticut valley is in some ways of similar structure, being broken by long parallel faults into narrow blocks or slabs, every block being tilted from its original position. Russell's description of the blocks in southern Oregon would apply nicely to those in Connecticut, except that the former have diverse displacements, while the latter all dip one way; but the Connecticut individual has, I feel confident, passed through one cycle of life and has entered well on a second; it has once been worn down nearly to base level since it was broken and faulted, and subsequent elevation at a rather remote period has allowed good advance in a repetition of this process. The general uniformity in the height of its trap ridges and their strong relief above the present broad valley bottom, require us to suppose this complexity of history. A given structure may therefore pass through two or more successive cycles of life, and before considering the resulting composite history in its entirety, it would be best to examine cases of simple development in a single cycle. After this is accomplished, it would be possible to recognize the incomplete partial cycles through which a structure has passed, and to refer every detail of form to the cycle in which it was produced.

The most elementary example that may be chosen to illustrate a simple cycle of geographic life is that of a plain, elevated to a moderate height above its base level. The case has already been referred to here and is given in more detail in an article printed in the proceedings of the American Association for the Advancement of Science, for 1884, to which I would now refer. When the succession of forms there described as developed at a given elevation over base level is clearly perceived, the occurrence of forms dependent on two different base levels in a single region can easily be recognized. The most striking example of such a complex case that I know of is that of the high plateaus of Utah, as described by Dutton. Northern New Jersey presents another example less striking but no less valuable: the general upland surface of the Highlands is an old base level, in which valleys have been cut in consequence of a subsequent elevation. The plateau developed on the tilted Triassic beds about Bound Brook is a second base level, cut during a halt in the rise from the previous lower stand of the land to its present elevation. There is a parable that illustrates the principle here presented.

An antiquary enters a studio and finds a sculptor at work on a marble statue. The design is as yet hardly perceptible in the rough cut block, from which the chisel strikes off large chips at every blow; but on looking closer the antiquary discovers that the block itself is an old torso, broken and weather beaten, and at once his imagination runs back through its earlier history. This is not the first time that the marble has lain on a sculptor's table, and suffered the strong blows of the first rough shaping. Long ago it was chipped and cut and polished into shape, and perhaps even set up in its completed form in some garden, but then it was neglected and badly used, thrown over and broken, till its perfect shape was lost, and it was sold for nothing more than a marble block, to be carved over again if the sculptor sees fit. Now it just beginning its second career. We may find many parallels to this story in the land about us, when we study its history through its form. The sequence of events and consequently of forms is so apparent here that no one could have difficulty in interpreting history from form, and it shall come to be the same in geography. The gorge of the Wissahickon through the highland northwest of Philadelphia can have no other interpretation than one that likens it to the first quick work of the sculptor on the old torso.

An essential as well as an advantage in this extension of the study of geography will be the definition of types and terms, both chosen in accordance with a rational and if possible a natural system of classification. Types and terms are both already introduced into geographic study, for its very elements present them to the beginner in a simple and rather vague way: mountains are high and rough; lakes are bodies of standing water, and so on. It is to such types and terms as these that every scholar must continually return as he reads accounts of the world, and it is to be regretted that the types are yet so poorly chosen and so imperfectly illustrated, and that the terms are so few and so insufficient. Physical geography is particularly deficient in these respects, and needs to be greatly modified in the light of the modern advance of topography. General accounts of continental homologies of course have their interest and their value, but they are of the kind that would associate whales with fishes and bats with birds. The kind of reform that is needed here may be perceived from that which has overtaken the biological sciences. The better teaching of these subjects lays representative forms before the student and requires him to examine their parts minutely. The importance of the parts is not judged merely by their size, but by their significance also. From a real knowledge of these few types and their life history it is easy to advance in school days or afterwards to a rational understanding of a great number of forms. Few students ever go so far in school as to study the forests of North America or the fauna of South America. It is sufficient for them to gain a fair acquaintance with a good number of the type forms that make up these totals. It is quite time that geography should as far as possible be studied in the same way. No school boy can gain a comprehensive idea of the structure of a continent until he knows minutely the individual parts of which continents are composed. No explorer can perceive the full meaning of the country he traverses, or record his observations so that they can be read intelligently by others until he is fully conversant with the features of geographic types and with the changes in their expression as they grow old. Both scholar and explorer should be trained in the examination and description of geographic types, not necessarily copies of actual places, before attempting to study the physical features of a country composed of a large number of geographic individuals. When thus prepared, geography will not only serve in geologic investigation, it will prosper in its proper field as well.

Geographic description will become more and more definite as the observer has more and better type forms to which he may liken those that he finds in his explorations, and the reader, taught from the same types, will gather an intelligent appreciation of the observer's meaning. Take the region north of Philadelphia above referred to. Having grown up upon it, I called it a hilly country, in accordance with the geographic lessons of my school days, and continued to do so for twenty years or more, until on opening my eyes its real form was perceived. It is a surface worn down nearly to a former base level but now diversified by ramifying valleys, cut into the old base level in consequence of a subsequent but not very ancient elevation of a moderate amount. Maturity is not yet reached in the present cycle of development, for there is still much of the old base level surface remaining, into which the valleys are gnawing their head ravines and thus increasing the topographic differentiation. Perhaps not more than a sixth of the total mass above present base level is yet consumed. To say that a country is hilly gives so wide a range to the imagination that no correct conception of it can be gained, but I venture to think that one who understands the terms used can derive a very definite and accurate conception from the statement that a certain country is an old, almost completed base level, raised from one to three hundred feet, and well advanced toward maturity in its present cycle of change.

It is from geographic methods thus conceived that geologic investigation will gain assistance. As the subject is properly developed it will form an indispensable part of the education of every explorer, topographer and geologist; and in its simpler chapters it will penetrate the schools. There is no other subject in which there is greater disproportion between the instruction, as commonly carried on, and the opportunity for application in after life. The intelligent part of the world is travelling from place to place to an extent that our fathers could not have believed possible, and yet not one person in ten thousand has any geographic instruction that enables him to see more than that a river is large or small, or that a hill is high or low. The meaning of geography is as much a sealed book to the person of ordinary intelligence and education as the meaning of a great cathedral would be to a backwoodsman, and yet no cathedral can be more suggestive of past history in its many architectural forms than is the land about us, with its innumerable and marvelously significant geographic forms. It makes one grieve to think of the opportunity for mental enjoyment that is lost because of the failure of education in this respect.

It may be asked perhaps how can one be trained in geographic types, seeing that it is impossible for schools to travel where the types occur. This is surely a great and inherent difficulty, but it may be lessened if it cannot be overcome. Good illustrations are becoming more and more common by means of dry plate photography; maps are improving in number and quality; but the most important means of teaching will be found in models. No maps, illustrations or descriptions can give as clear an idea of relief as can be obtained from a well-made model, and with a set of models, fifty or sixty in number, the more important types and their changes with age can be clearly understood. Maps, illustrations and descriptions supplement the models. The maps should be contoured, for in no other way can the quantitative values be perceived that are essential to good study. The illustrations should be of actual scenes; or, if designs, they should be designed by a geographic artist. The descriptions should wherever possible be taken from original sources, in which the narrator tells what he saw himself. It is, to be sure, not always possible to know what kind of a form he describes, owing to lack of technical terms, but many useful examples can be found that may then be referred to their proper place in the system of geographic classification that is adopted.

I shall consider only one example in detail to show how far short, as it seems to me, geography fails of its great opportunity, both as taught in schools and as applied in after life.

In northeastern Pennsylvania there are several water-falls that leap over tilted beds of rock. Such falls are known to be of rare occurrence, and we may therefore inquire into the cause of their rarity and the significance of their occurrence in the region referred to.

We may first look at the general conditions of the occurrence of water-falls. They indicate points of sharply contrasted hardness in the rocks of the stream channel, and they show that the part of the channel above the fall has not yet been cut down to base level. When the channel reaches base level there can be no falls. Now it is known from the general history of rivers that only a short part of their long lives is spent in cutting their channels down to base level, except in the case of headwater streams, which retain youthful characteristics even through the maturity of their main river. Consequently, it is not likely that at any one time, as now, in the long lives of our many rivers, we should see many of them in their short-lived youthful phase. Falls are exceptional and denote immaturity. They endure a little longer on horizontal beds, which must be cut back perhaps many miles up stream before the fall disappears, than on tilted beds, which must be cut down a few thousand feet at most to reduce them to base level. Falls on tilted beds are therefore of briefer duration than on horizontal beds, and are at any time proportionately rarer. On the headwater branches of a river where youthful features such as steep slope and sudden fall remain after the main river has a well-matured channel, we sometimes find many water-falls, as in the still young branches of the old Ohio. These are like young twigs on an old tree. But even here the rocks are horizontal, and not tilted as in the cases under consideration.

The falls of such headwater streams must persist until the plateau is cut away, for the cap rocks over which the streams leap being horizontal cannot be smoothed down till the whole plateau is cut through. They are long-lived features. Moreover every one of the innumerable branch streams must on its way down from the uplands fall over the outcropping edges of all the hard beds. The falls will therefore be common as well as long-lived features. Their frequent occurrence confirms the correctness of this generalization. On the other hand, in regions of tilted rocks, the hard beds are avoided by the streams, which select the softer strata for their valleys. The hard beds soon stand up as ridges or divides, across which only the large streams can maintain their courses, and these are the very ones that soon cut down any fall that may appear in their early stages. Falls on tilted rocks are therefore rare not only because of their brief duration, but also because tilted rocks are crossed by few streams, except the large ones, which soon cut away their falls.

The foregoing considerations show clearly enough that falls like those of northeastern Pennsylvania are rare, and we have now to consider why they should be prevalent in the region in question. The Appalachians contain many water-gaps cut down on tilted beds, every one of which may have been the site of a fall for a relatively brief period of river immaturity, but this brief period is now left far in the past. The streams show many signs of maturity: their slope is gentle and their valleys are wide open from Alabama to Pennsylvania, but in the northeastern corner of the latter State we find a group of streams that leap over high benches into narrow gorges, and the benches are held up by tilted rocks. Manifestly the streams have in some way been lately rejuvenated; they have been, in part of their courses at least, thrown back into a condition of immaturity, at a time not long past, and, as has so well been shown by White, the cause of this is the obstruction of their old channels by irregular deposits of glacial drift. Here first in the whole length of the Allegheny section of the Appalachians we find an exceptional condition of stream life, and here also we come into a region lately glaciated, where heaps of drift have thrown the streams out of their old tracks. The explanation fits perfectly, and if it had not been discovered by inductive observation in the field, the need of it might have been demonstrated deductively. It is a case that has given me much satisfaction from the promise that it holds out of a wide usefulness for geography, when its forms are systematically studied and its principles are broadly applied.

A final word as to terminology. The material common to geography and geology may be included under the name physiography, as used by Huxley. It is, I think, a subject that is destined to receive much attention. Physical geography, as ordinarily defined, does not cover the ground that it might fairly claim. It is too largely descriptive and statistical. Geographic evolution, as defined by Geikie, is the general preparation of existing geography by geologic processes. It does not consider the general scheme of topographic development or the natural classification of geographic forms.

It is not easy to change the accepted meaning of a term, and I would therefore suggest that a new term should be introduced to include the classification of geographic forms, as advocated here, rather than that any old and accepted term should be stretched over a new meaning. As the essential of the study here outlined is the systematic relation of form to structure, base level and time, the new term might be Systematic Geography.

THE CLASSIFICATION OF GEOGRAPHIC FORMS BY GENESIS.

BY W. J. MCGEE.

Scientific progress may be measured by advance in the classification of phenomena. The primitive classification is based on external appearances, and is a classification by analogies; a higher classification is based on internal as well as external characters, and is a classification by homologies; but the ultimate classification expresses the relations of the phenomena classified to all other known phenomena, and is commonly a classification by genesis.

The early geologic classification was based chiefly upon simple facts of observation; but with continued research it is found that the processes by which the phenomena were produced may be inferred, and, accordingly, that the phenomena may be grouped as well by the agencies they represent as by their own characteristics. Thus the empiric or formal laws of relation give place to philosophic or physical laws indicating the casual relations of the phenomena, and the final arrangement becomes genetic, or a classification by processes rather than products.

The phenomena of geography and geology are identical, save that the latter science includes the larger series: since the days of Lyell the geologist has seen in the existing conditions and agencies of the earth a reflection and expression of the conditions under which and the agencies by which its development has been effected; the far stretching vista of geologic history is illuminated only by knowledge of the earth of to-day; and the stages in geologic development are best interpreted in terms of geography. So a genetic classification of geologic phenomena (which is rendered possible and intelligible through geographic research) will apply equally to geography, whether observational or of the more philosophic nature which Davis proposes to call Systematic Geography, and which Powell has called Geomorphology. Such a classification is here outlined.

The various processes or movements with which the geologist has to deal fall naturally into two principal and antagonistic categories and five subordinate categories; and each category, great and small, comprises two classes of antagonistic processes or movements.

The initial geologic movements (so far as may be inferred from the present condition of the earth) were distortions or displacements of the solid or solidifying terrestrial crust, occurring in such manner as to produce irregularities of surface. These are the movements involved in mountain growth and in the upheavel of continents. They have been in operation from the earliest known eons to the present time, and their tendency is ever to deform the geoid and produce irregularity of the terrestrial surface. The movements have been called collectively "displacement" and "diastrophism," but in the present connection they may be classed as diastatic, or, in the substantive form, as deformation. Recent researches, mainly in this country, have indicated that certain diastatic movements are the result of transference of sediment—that areas of loading sink, and areas of unloading rise; but it is evident that the transference of sediment is itself due to antecedent diastatic movements by which the loaded areas were depressed and the unloaded areas elevated; and the entire category may accordingly be divided into antecedent and consequent diastatic movements. A partially coincident division may be made into epeirogenic, or continent-making movements (so called by Gilbert), and orogenic, or mountain-making movements. Though there is commonly and perhaps always a horizontal component in diastatic movement, the more easily measured component is vertical, and when referred to a fixed datum (e.g. sea level) it is represented by elevation and depression.

The second great category of geologic processes comprehends the erosion and deposition inaugurated by the initial deformation of the terrestrial surface. By these processes continents and mountains are degraded, and adjacent oceans and lakes lined with their debris. They have been in active operation since the dawn of geologic time, and the processes individually and combined ever tend to restore the geoid by obliterating the relief produced by deformation. The general process, which comprises degradation and deposition, may be called gradation.

The first subordinate category of movements is allied to the first principal category, and comprises, (1) the outflows of lavas, the formation of dykes, the extravasation of mineral substances in solution, etc., (2) the consequent particle and mass movements within the crust of the earth, and (3) the infiltration of minerals in solution, sublimation, etc.,—in short, the modification of the earth's exterior directly and indirectly through particle movements induced by the condition of the interior. These processes have been in operation throughout geologic time, though they perhaps represent a diminishing series; they have added materially to the superficial crust of the earth; and it is fair to suppose that they have modified the geoid not only by additions to the surface but by corresponding displacements in their vicinity. The category may be tentatively (but rather improperly) called vulcanism, and the antagonistic classes of movements constituting it are extravasation and its antithesis. The vibratory movements of seismism probably result from both deformation and vulcanism under certain conditions.

The second subordinate category of processes is closely linked with all of the others. It comprises the various chemic and chemico-mechanical alterations in constitution and structure of the materials of the earth's crust. The processes have affected the rocks ever since the solidification of the planet, though probably in a progressively diminishing degree; and they have materially (but indirectly rather than directly) modified the internal constitution and external configuration of the earth. The processes may be collectively called alteration; and the antagonistic classes into which the category is divisible are lithifaction and decomposition in their various phases, or rock-formation and rock-destruction.

The third subordinate category of processes, viz: glaciation, is related to the second principal category; but since (1) it is probable if not actually demonstrable that under certain circumstances glacial grinding tends to accentuate preëxisting irregularities of surface, and since (2) it is well known that glacial deposition sometimes gives great irregularity of surface, it is evident that glaciation is not a simple process of gradation, but must be clearly distinguished therefrom. A considerable portion of the earth's surface has been modified by glaciation during later geologic times. The general process comprises glacial construction and glacial destruction.

There is a fourth subordinate category of processes, which is also allied to gradation, viz: wind-action, which may be made to include the action of waves and wind-born currents; but since the winds scoop out basins and heap up dunes, while the waves excavate submerged purgatories and build bars, it is evident that this category, too, must be set apart. The processes are only locally important as modifiers of the land surface of the globe. They comprise constructive action and destructive action.

There is a final category which is in part allied to alteration but is in part unique, viz: the chemic, mechanical, and dynamic action of organic life. Ever since the terrestrial crust become so stable as to retain a definite record of the stages of world-growth, life has existed and by its traces has furnished the accepted geologic chronology: at first the organisms were simple and lowly, and affected the rocks chemically through their processes of growth and decay, as do the lower plants and animals of the present; later, certain organisms contributed largely of their own bodily substance to the growing strata; and still later, the highest organisms, with man at their head, have by dynamic action interfered directly with gradation, alteration, and wind-action, and thus, perhaps, indirectly with the more deep-seated processes of world growth. The vital forces are too varied in operation to be conveniently grouped and named.

These categories comprise the various processes contemplated by the geologist, and collectively afford an adequate basis for a genetic classification of geologic science. Their relations are shown in the accompanying table:

Classification of Geologic Processes.

Principal Categories. 1.—Deformation. Antecedent<Epeirogenic. Consequent>Orogenic. Elevation. Depression.

2.—Gradation Deposition. Degradation.

Subordinate Categories. 1.—Vulcanism. Extravasation. (Antithesis of Extrav.)

2.—Alteration. Lithifaction. Decomposition.

3.—Glaciation. Glacial construction. Glacial destruction.

4.—Wind action. Wind construction. Wind destruction.

5.—Vital action. Various constructive and destructive processes.

On applying this classification to geographic forms, the various phenomena immediately fall into the same arrangement. The continents, great islands, mountain systems, and non-volcanic ranges and peaks generally, the oceans, seas, and some bays, gulfs and lakes, evidently represent the diastatic category of movements. These greater geographic features have long been named and classified empirically, and can be referred to their proper places in a genetic taxonomy without change in terminology. The volcanoes, craters, calderas, lava fields, tuff fields, tufa crags, mesas, volcanic necks, dykes, etc., however modified by degradation, alteration, glaciation, or wind action, exhibit characteristic forms which have often received names indicative of their origin. The glacial drift with its various types of surface, the moraines, drumlins, kames, roches de moutonnées, rock basins, kettles, lacustral plains, aqueo-glacial terraces, loess hills and plains, etc., have been studied in their morphologic as well as their structural aspects, and the elements of the configuration commonly assumed have been described, portrayed, and appropriately named; and they take a natural place in the classification of products by the processes giving rise to them. The dunes, dust drifts, sand ridges, etc., and the wind-scooped basins with which they are associated, are local and limited, but are fairly well known and fall at once into the genetic classification of forms and structures. But all of these geographic forms are modified, even obliterated, by the ever prevailing process of gradation, which has given origin to nearly all of the minor and many of the major geographic forms of the earth. The forms resulting from this second great category of geologic processes have generally engaged the attention of systematic students, but their prevalence, variety and complexity of relation are such that even yet they stand in greatest need of classification.

Lesley thirty years ago regarded the mountain as the fundamental topographic element; Richthofen recognizes the upland and the plain ("aufragendes Land und Flachböden") as the primary classes of configuration comprehending all minor elements of topography; Dana groups topographic forms as (1) lowlands, (2) plateaus and elevated table lands, and (3) mountains; and these related allocations are satisfactory for the purposes for which they are employed. But the implied classification in all these cases is morphologic rather than genetic, and is based upon superficial and ever varying if not fortuitous characters; and if it were extended to the endless variety of forms exhibited in the topography of different regions it would only lead to the discrimination of a meaningless multitude of unrelated topographic elements.

In an exceedingly simple classification of geographic phenomena, the primary grouping is into forms of construction and forms of destruction; but it is evident on inspection of the table introduced above that such a classification is objectionable unless the greater geographic elements due to diastatic movements (in which the constructive action is veritable but different in kind from those in the other categories) be excluded, and this is impracticable without limiting the classification to subordinate phenomena. Moreover it is illogical and useless to unite the constructive phenomena of the remaining categories, since (1) the processes exemplify widely diverse laws, which must find expression in any detailed classification whether genetic or not, and since (2) the differences between the forms united are much greater than the differences between the forms separated in such a classification—e.g. the differences between a dune, a drumlin and a mesa (all constructive forms) are far greater than the differences between a fresh lava sheet and a deeply cut mesa, between a drumlin and the smallest drift remnant, or between a dune and a Triassic mound of circumdenudation; and this is true whether the distinction be made on analogic, homologic, or genetic grounds. Indeed it seems evident that while discrimination of constructive and destructive forms is necessary and useful in each genetic category, the use of this distinction as a primary basis of classification is inexpedient.

The classification of topographic forms proposed a few years ago by Davis, who regards "special peculiarities of original structure" as a primary, and "degree of development by erosion" a secondary basis, and Richthofen's arrangement of categories of surface forms as (1) tectonic mountains, (2) mountains of abrasion, (3) eruptive mountains, (4) mountains of deposition, (5) plains, and (6) mountains of erosion,¹ in addition to depressions of the land (Die Hohlformen des Festlandes), are more acceptable, since they are based in part on conditions of genesis. But it is clearly recognized by modern students of dynamic geology that waterways are the most persistent features of the terrestrial surface; and the most widely applicable systems of classification of the surface configuration of the earth thus far proposed have been based substantially on the agencies of gradation. Thus Powell, Löwl and Richthofen classify valleys by the conditions of their genesis; Gilbert classifies drainage; and Phillipson, unduly magnifies the stability and genetic importance of the water parting, classifies the hydrography through the divides; and, although these geologists have not dwelt upon and perhaps have failed to perceive the relation, the same classification is as applicable to every feature of the local relief as to the streams by which the relief was developed.

¹ (1) Tektonische Gebirge, (2) Rumpfgebirge oder Abrasionsgebirge, (3) Ausbruchsgebirge, (4) Aufschüttungsgebirge, (5) Flachböden, und (6) Erosionsgebirge.

In a general classification of the topographic forms developed through gradation, it would be necessary to include the forms resulting from deposition as well as degradation, and also to discuss the relation of base-level plains to antecedent and consequent relief; but in a brief résumé it will suffice to consider only the modifications produced by degradation upon a surface of deposition after its emergence from beneath water level as a regular or irregular terrane; and the influence of base-level upon the topographic forms developed upon such a surface may be neglected in a qualitative discussion, though it is quite essential in quantitative investigation.

The hydrography developed upon terranes affected by displacement both before and after emergence has already been satisfactorily classified. Powell, years ago, denominated valleys established previous to displacement of the terrane by faulting or folding, antecedent valleys; valleys having directions depending on displacement, consequent valleys; and valleys originally established upon superior and subsequently transferred to inferior terranes, superimposed valleys; and these valleys were separated into orders determined by relation to strike and again into varieties determined by relation to subordinate attitude of the terranes traversed. Gilbert adopted the same general classification, and so extended as to include certain special genetic conditions. Tietze, in the course of his investigation of the Sefidrud (or Kizil Uzen) and other rivers in the Alburs mountains of Persia, independently ascertained the characteristics of the class of waterways comprehended by Powell under the term antecedent; Medlicott and Blanford observed that many of the Himalayan rivers are of like genesis; and Rütimeyer, Peschel and others have recognized the same genetic class of waterways; but none of these foreign geologists have discussed their taxonomic relations. Löwl, who upon a priori grounds denies the possibility of antecedent drainage, has recently developed an elaborate taxonomy of valleys which he groups as (a) tectonic valleys, and (b) valleys of erosion (Erosionsthäler). The first of these categories is separated into two classes, viz: valleys of flexure and valleys of fracture, and these in turn into several sub-classes determined by character of the displacement and its relations to structure; and the second, whose genesis is attributed to retrogressive ("rückwärts fortschreitende" or "rückschreitende") erosion, is vaguely separated into several ill-defined classes and sub-classes determined by structure, climate, and various other conditions. The second of Löwl's categories is also recognized by Phillipson. Still more recently, Richthofen, neglecting antecedent drainage, designated the superimposed class of Powell epigenetic, and formulated a classification of the remaining types of continental depressions (Die Hohlformen des Festlandes) as (a) orographic depressions (Landsenken); (b) tectonic valleys, and (c) sculptured valleys; and the last two categories are separated into classes and sub-classes, corresponding fairly with those of Löwl, determined by their relations to structure and by various genetic conditions.

These several classifications have much in common; their differences are largely due to the diversity of the regions in which the investigations of their respective authors have been prosecuted; but combined they probably comprehend all the topographic types which it is necessary to discriminate.

The American classification and nomenclature, particularly, is unobjectionable as applied to montanic hydrography; but it does not apply to the perhaps equally extensive drainage systems and the resulting topographic configuration developed on emergent terranes either (a) without localized displacement or (b) with localized displacement of less value in determining hydrography than the concomitant erosion, terracing and reef building; neither does it apply to the minor hydrography in those regions in which the main hydrography is either antecedent or consequent; nor does it apply even to the original condition of the superimposed or antecedent drainage of montainous regions.

Upon terranes emerging without displacement and upon equal surfaces not yet invaded by valleys, the streams depend for their origin on the convergence of the waters falling upon the uneroded surface and affected by its minor inequalities, and for their direction upon the inclination of that surface. They are developed proximally (or seaward) by simple extension of their courses by continued elevation, and distally by the recession of the old and the birth of new ravines; and since in the simple case it follows from the law of probabilities that the receding ravine will retain approximately the old direction and that the new ravines will depart therefrom at high angles, the drainage systems thus independently developed become intricately but systematically ramified and more or less dendritic in form. Löwl, Phillipson, Richthofen, and other continental, as well as different British and Indian geologists, and Lesley in this country, indeed recognize this type of drainage, but they do not correlate it with the montanic types; and Löwl's designation, derived from the manner in which he conceives it to be generated ("rückschreitende Erosion"), does not apply to either the completed drainage, or the coincident topography.

Although its subordinate phases are not yet discriminated on a genetic basis, this type or order of drainage is sufficiently distinct and important to be regarded as coördinate with the type represented by the entire group of categories recognized by Powell and clearly defined by Gilbert. Such hydrography (which either in its natural condition or superimposed characterizes many plains, some plateaus, and the sides of large valleys of whatever genesis) may be termed autogenous; while the drainage systems imposed by conditions resulting from displacement (which characterize most mountainous regions) may be termed tectonic. Gilbert's classification of drainage may then be so extended as to include topography as well as hydrography, and so amplified as to include the additional type.

Drainage systems and the resulting systems of topography (all of which belong to the degradational class of forms) are accordingly.—

Type 1, Autogenous.

Type 2, Tectonic—

Order A, Consequent, upon

Class a, Displacement before emergence, and

Class b, Sudden displacement after emergence;

Order B, Antecedent; and

Class a, Sedimentation (when the superimposed drainage may be autogenous),

Class b, Alluviation or subaerial deposition, and

Class c, Planation (in which two cases the superimposed drainage may simulate the autogenous type).

In brief, the entire domain of geologic science is traversed and defined by a genetic classification of the phenomena with which the geologist has to deal; and the same classification is equally applicable to geographic forms, as the accompanying table illustrates:

Representative Geographic Forms as classified by Genesis.

GENETIC PROCESSES. GEOGRAPHIC FORMS.

Category. Class.

DEFORMATION ELEVATION Continents, great islands, most mountain ranges, etc., not classified in detail.

DEPRESSION Oceans, great seas and bays, some inland valleys and lake-basins, etc., not classified in detail.

GRADATION DEPOSITION Newly emerged ocean-bottoms (e.g., portions of the Coastal plain), playas and mountain-bound deserts, many flood-plains, marshes, etc., not classified in detail.

DEGRADATION Drainage-systems and resulting topographic elements which are— 1—Autogenous (not classified in detail); and 2—Tectonic— Consequent, upon Displacement before emergence, and Sudden displacement after emergence; Antecedent; and Superimposed, through Sedimentation, Alluviation, and Planation.

VULCANISM EXTRAVASATION Volcanic peaks, craters, lava-fields, tufa-crags, sinter-cones, volcanic necks, mesas, dykes, some mineral veins, etc., not classified in detail.

(ANTITHESIS OF DO.) Sinks, caverns, some fissures, etc., not classified in detail.

ALTERATION LITHIFICATION Minor features of certain topographic forms, e.g., reefs, crags, pinnacles, salients, out-cropping veins, some cataracts, etc., not classified in detail.

DELITHIFICATION Minor features of certain topographical forms, e.g., pools and basins, reëntrants, some fissures and caverns, etc., not classified in detail.

GLACIATION GLACIAL CONSTRUCTION Drift-plains, moraines of whatever character, drumlins, kames, aasar, drift-dammed lakes, loess-plains and ridges, etc., not classified in detail.

GLACIAL DESTRUCTION Rock-basins, U-cañons, roches de moutonnées, etc., not here classified in detail.

WIND ACTION WIND CONSTRUCTION Dunes, sand-ridges, bars, spits, etc., not here classified in detail.

WIND DESTRUCTION Ponds associated with dunes, "blow-outs," "purgatories," etc., not classified in detail.

VITAL ACTION (Not discriminated)

THE GREAT STORM OF MARCH 11–14, 1888.

A SUMMARY OF THE REMARKS MADE BY BRIGADIER-GENERAL A. W. GREELY, CHIEF SIGNAL OFFICER OF THE ARMY.

This storm is by no means as violent as others which have occurred in the eastern part of the United States. It is noted, however, as being one in which an unusual amount of snow fell, which, drifted by the high winds caused by the advance of an anticyclonic area in rear of the storm depression, did an enormous amount of damage to the railways in Massachusetts, southern New York, and New Jersey.

The storm centre was first noticed in the North Pacific on March 6th; whence it passed southeast from the Oregon coast to northern Texas by the 9th. The centre instead of maintaining the usual elliptical form, gradually shaped itself into an extended trough of low pressure, which covered the Mississippi and Ohio valleys during the 10th. On the morning of March 11th the barometer trough extended from Lake Superior southward to the eastern part of the Gulf of Mexico; in the northern section over Lake Superior, and the southern part, over Georgia, distinct centres, with independent wind circulation, had formed.

The northern storm centre moved northeastward and disappeared, while the southern centre moved slowly eastward, passing off the Atlantic coast near Cape Hatteras. The pressure on the afternoon of March 11th was about 29.07 at the centre of both the northern and southern storms, but during the night of the 11–12th the pressure decreased in the southern storm centre, and the area instead of continuing its easterly direction moved almost directly to the north, and on the morning of March 12th was central off the New Jersey coast.

The causes which underlie the decrease of pressure and consequent increase in the violence of storms are, as yet, undetermined. The theory of "surges," that is, atmospheric waves independent of the irregular variations consequent on storms, has been urged by some, and especially by Abercromby, as the cause of the deepening of depressions in some cases or of increasing the pressure in other cases. It is possible that under this theory a "surge," passing over the United States to the eastward, as its trough became coincident with the centre of low pressure increased its intensity or decreased its pressure, and the consequent increase in barometric gradients added to the violence of the winds. It should be pointed out, however, that the very heavy rainfalls from Philadelphia southward to Wilmington during the 11th, and even the heavier ones over the lower valley of the Hudson and in Connecticut during the 12th, may have exercised a potent influence in depressing the barometer at the centre of this storm. However this may be, it is certain that the storm remained nearly stationary, with steadily decreasing pressure until midnight of March 12th, at which time it was central between Block Island and Wood's Holl, with an unusually low barometer of 28.92 at each station. During this day the winds were unusually high along the Atlantic coast from Eastport to Norfolk; the maximum velocities at the various stations ranging from 48 miles at New York City and New Haven to 60 miles at Atlantic City and 70 miles per hour at Block Island. These winds, though high, are not unprecedented, and if they had been accompanied only by precipitation in the form of rain, the damage on land would have been inconsiderable, but, unfortunately for the commercial interests of New York and other neighboring great cities, the passage of the low area to the eastward was followed by a cold wave of considerable severity and of unusual continuance.

The northern storm centre, which had passed eastward on the 11th, had had the usual effect of drawing in a large quantity of cold air from British America; a cold wave following the wake of this storm, as is usual during the winter season. This usual effect was intensified by the advance of a second, and more violent, cyclonic centre northward; the effect of which was to augment the cold wave already in progress by drawing in a still larger amount of cold air to re-enforce it.

As has been already alluded to, the quantity of snowfall was unusually great. The easterly and northeasterly winds had drawn a large amount of aqueous vapor from the Atlantic over New England in advance of the low area. The sudden change of temperature precipitated by far the greater portion of the aqueous vapor in the air, with the result of an almost unprecedented fall of snow over western Massachusetts, Connecticut, and the valley of the Hudson.

Professor Winslow Upton, Secretary of the New England Meteorological Society, has gathered estimates of snow from 420 different observers, which go to show that 40 inches or more of snow fell over the greater part of the districts named.

The deepening of the area of low pressure and the augmentation of the cold high area advancing from British America resulted in barometric gradients of unusual intensity; there being gradients in excess of 6, when gradients of 5 rarely occur either in the United States or Great Britain. The high winds caused by these unusual gradients had the effect of drifting the snow to an unusual extent, so that, as is well known, nearly every railroad in New Jersey, Connecticut, New York, and Massachusetts was snow-bound; the earliest and most prolonged effects being experienced in Connecticut, which doubtless received the full benefit of the heavy snowfall in the Hudson River valley in addition to that in the western part of that State.

It is thought by some that the storm re-curved and passed northwest into Connecticut; an opinion in which I cannot concur. The international map and reports tend to show that this storm passed northeastward and was on the Banks of Newfoundland on the 17th of March. The peculiar shape of the isobars, while the storm could be clearly defined from observations at hand, was such that it is not unreasonable to believe that the change of wind to the south at Block Island was due simply to an off-shoot of the storm from the main centre, in like manner as the storm itself was the outgrowth of a previous depression.

The track of this storm across the sea is left to Professor Hayden. These remarks are necessarily imperfect, as my official duties have been such as to prevent any careful study or examination of the storm apart from that possible on the current weather maps of the Signal Service.

THE GREAT STORM OFF THE ATLANTIC COAST OF THE UNITED STATES, MARCH 11TH–14TH, 1888.

BY EVERETT HAYDEN, In charge of the division of Marine Meteorology, Hydrographic Office, Navy Dept.

INTRODUCTION.

The history of a great ocean storm cannot be written with any completeness until a long interval of time has elapsed, when the meteorological observations taken on board hundreds of vessels of every nationality, scattered over the broad expanse of ocean, and bound, many of them, for far distant ports, can be gathered together, compared, and, where observations seem discordant, rigidly analyzed and the best data selected. It is only when based upon such a foundation that the story can fully deserve the title of history, and not romance, fact and not hypothesis. At best, there must be wide areas where the absence of vessels will forever leave some blank pages in this history, while elsewhere, along the great highways of ocean traffic, the data are absolutely complete. Last August a tropical hurricane of terrific violence swept in toward our coast from between Bermuda and the Bahamas, curved to the northward off Hatteras, and continued its destructive course past the Grand Banks toward northern Europe; hundreds of reports from masters of vessels enabled us accurately to plot its track, a great parabolic curve tangent to St. Thomas, Hatteras, Cape Race, and the northern coast of Norway. Six months later a report forwarded by the British Meteorological Office, from a vessel homeward bound from the Equator, indicated that it originated far to the eastward, off the coast of Africa, and only the other day the log of a ship which arrived at New York, March 30th, from Calcutta, supplied data by means of which the storm track can be traced still more accurately, westward of the Cape Verde islands. Not only that, but this same vessel on the 11th of March was about 500 miles to the eastward of Bermuda, and, while the great storm was raging between Hatteras and Sandy Hook, was traversing a region to the northeastward of Bermuda from which our records are as yet very incomplete. It will thus be clearly understood that while the most earnest efforts have been made, not only to collect and utilize all available information, but to be careful and cautious in generalizing from the data at hand, yet this study must be considered as only preliminary to an exhaustive treatise based on more complete data than it is now possible to obtain.

Four charts have been prepared to illustrate the meteorological conditions within the area from 25° to 50° north latitude, 50° to 85° west longitude, at 7 A.M., 75th meridian time, March 11th, 12th, 13th and 14th respectively. Data for land stations have been taken from the daily weather maps published by the U. S. Signal Service, and the set of tri-daily maps covering the period of the great storm has been invaluable for reference throughout this discussion. Marine data are from reports of marine meteorology made to this office by masters of vessels, and not only from vessels within the area charted, but from many others just beyond its limits. The refined and accurate observations taken with standard instruments at the same moment of absolute time all over the United States by the skilled observers of the Signal Service, together with those contributed to the Hydrographic Office by the voluntary co-operation of masters of vessels of every nationality, and taken with instruments compared with standards at the Branch Hydrographic Offices immediately upon arrival in port, make it safe to say that never have the data been so complete and reliable for such a discussion at such an early date.

It will not be out of place briefly to refer to certain principles of meteorology that are essential to a clear understanding of what follows. The general atmospheric movement in these latitudes is from west to east, and by far the greater proportion of all the areas of low barometer, or centers of more or less perfectly developed wind systems, that traverse the United States, move along paths which cross the Great Lakes, and thence reach out over the Gulf of St. Lawrence across the Atlantic toward Iceland and northern Europe. Another very characteristic storm path may also be referred to in this connection, the curved track along which West Indian hurricanes travel up the coast. The atmospheric movement in the tropics is, generally speaking, westward, but a hurricane starting on a westward track soon curves off to the northwest and north, and then getting into the general eastward trend of the temperate zone, falls into line and moves off to the northeast, circling about the western limits of the area of high barometer which so persistently overhangs the Azores and a great elliptical area to the southwestward. The circulation of the wind about these areas of low barometer, and the corresponding changes of temperature, are indicated graphically on the map: the isobars, or lines of equal barometric pressure, are, as a rule, somewhat circular in form, and the winds blow about and away from an area of "high" in a direction with the hands of a watch (in nautical parlance, "with the sun"), toward and about "low" with an opposite rotary motion, or against the hands of a watch; in front of a "low" there will therefore be, in extra tropical latitudes, warm southeasterly winds, and behind it cold northwesterly winds, the resulting changes of temperature being shown by the isotherms, or lines of equal temperature. Moreover, in a cyclonic system of this kind the westerly winds are generally far stronger than the easterly winds, the motion of the whole system from west to east increasing the apparent force of the former and decreasing that of the latter. Upon reaching the coast, such areas of low barometer, or storm systems, almost invariably develop a great increase of energy, largely due to the moisture in the atmosphere overhanging the ocean, which, when the air is chilled by contact with the cold dry air rushing in from the "high," is precipitated and becomes visible in the form of clouds, with rain or snow. The latent heat liberated by the condensation of this aqueous vapor plays a most important part in the continuance of the storm's energy and, indeed, in its increase of energy: the warm light air flowing in towards the central area of the storm rises rapidly into regions where the pressure is less, that is, where the thickness and consequently the weight of the superincumbent atmosphere is less; it therefore rapidly expands, and such expansion would result in a much more rapid cooling, and a corresponding decrease in its tendency to rise still higher, were it not for the latent heat liberated by the condensation of the moisture which it contains. Thus the forces that are conspiring to increase the energy of the storm are powerfully assisted by the presence and condensation of aqueous vapor, and the increasing updraught and rarefaction are at once marked by the decreasing barometric pressure at the center. For example, a storm was central over the Great Lakes on Jan. 25th, with lowest barometer 29.7; the following day it was central off Nantucket, barometer 29.2; and on the 27th and 28th, over the Gulf of St. Lawrence, with barometer below 28.6. But such instances are so common as to make it the rule, and not the exception. As stated above, the isobars about an area of low barometer are somewhat circular in form; more strictly speaking, they are somewhat oval or elliptical in shape, and the more elongated the north and south axis of this ellipse, the greater the resulting changes of temperature, because, as it moves along its broad path toward the Atlantic, the indraught, or suction, is felt in front far down toward the tropics, and in rear far to the northward, beyond the territorial limits of the United States.

Similarly with regard to the general movement of areas of high barometer, certain laws of motion have been clearly established by means of studies of the daily international charts; instead of a motion toward east-northeast, these areas when north of the 40th parallel, have in general a motion towards east-southeast, and as a rule move more rapidly and with greater momentum than "lows," so that they may be said to have the right of way, when the tracks of two such systems converge or intersect. These laws, or at least that relating to the Great Lake storm track, as it may be called, soon become evident to anyone who watches the weather map from day to day, upon which are charted the systems of low and high barometer as they follow one another across the continent, bringing each its characteristic weather.

MARCH 11TH, 7 A.M.

The first of the accompanying weather charts indicates graphically the meteorological conditions over the wide area charted, comprising about 3,000,000 square miles, of which one-third is land and two-thirds water. Over the land there is a long line, or trough, of low barometer, extending from the west coast of Florida up past the eastern shore of Lake Huron, and far northward toward the southern limits of Hudson Bay. In front of this advancing line the prevailing winds are southeasterly, and the warm moist air drawn up from southern latitudes spreads a warm wave along the coast, with generally cloudy weather and heavy rains, especially south of Hatteras; the Signal Service observer at Pensacola, for example, reports the heavy rain-fall of 4.05 inches on the 10th. About midway of this trough of low barometer there is a long narrow region of light variable winds; of rapid changes in meteorological conditions; calms, shifts of wind, intervals of clearing weather; then overcast again, with cooler and fresh northwesterly winds, increasing to a gale. The front line of this advancing battalion of cold northwesterly winds is more than a thousand miles in length, and covers the whole breadth of the United States: its right flank is on the Gulf, its left rests on the Great Lakes, or even farther north; the temperature falls rapidly at its approach, with frost far south into Louisiana and Mississippi, and heavy snow in central Kentucky and eastern Tennessee. The long swaying line is advancing toward the coast at the rate of about 600 miles a day, followed by a ridge of high barometer reaching from Texas to Dakota and Manitoba. At points along the trough the barometer ranges from 29.70, a hundred miles north of Toronto, to 29.86 at Pittsburg, 29.88 at Augusta, and 29.94 at Cedar Keys. Along the ridge the barometer is very high; 30.7 to the northward about Lake Winnipeg, 30.6 in Wyoming, 30.7 in Indian Territory, and 30.5 south of the Rio Grande. The difference of pressure from trough to ridge is thus measured by about an inch of mercury in the barometer. Moreover, the chart shows that there is another ridge of high barometer in advance, curving down off the coast from northern Newfoundland, where the pressure is 30.6, toward Santo Domingo, where the pressure is 30.3, and passing midway between Hatteras and Bermuda. Farther to the eastward the concentric isobars show the presence of a storm which originated about Bermuda on the 9th, and is moving off toward Europe where, in a few days, it may cause northwesterly gales with snow to the northward of its track, and southeasterly gales with rain to the southward. Storm reports from various vessels show that this storm was of hurricane violence, with heavy squalls and high seas, but it need not be referred to in this connection further than to say that it sent back a long rolling swell from northeast, felt all along the Atlantic sea-board the morning of the 11th, and quite distinct from that caused by the freshening gale from the southeast.