Astronomical Vistas.

THE CENTURY OF ASTEROIDS.

The nineteenth century may be called the Age of the Asteroids. It was on the first night of this century that the first asteroid was discovered! Through all the former ages, no man on the earth had had definite knowledge of the existence of such a body. It was reserved for Guiseppe Piazzi, an Italian astronomer at Palermo, to make known by actual observation the first member of the planetoid group. If human history had the slightest regard for the calendars of mankind—if the eternal verities depended in any measure on the almanac or the division of time into this age or that—we might look with wonder on the remarkable coincidence which made the discovery of the first asteroid to happen in the first evening twilight of the first day of the nineteenth century!

At the close of the eighteenth century, mankind were acquainted with all the major planets except Neptune. Uranus, the last of the group, was discovered by the Elder Herschel, on the night of the thirteenth of March, 1781. True, this planet had been seen on twenty different occasions, by other observers; but its character had not been revealed. Sir William called his new world Georgium Sidus, that is, the George Star, in honor of the King of England. The world, however, had too much intelligence to allow the transfer of the name of George III. from earth to heaven. Such nomenclature would have been unpopular in America! The name of the king was happily destined to remain a part of terrestrial history!

For a while it was insisted by astronomers and the world at large that the new globe, then supposed to bound the solar system on its outer circumference, should be called Herschel, in honor of its discoverer. But the old system of naming the planets after the deities of classical and pagan mythology prevailed; and to the names of Mercury, Venus, Mars, Jupiter, Saturn, was now added the name Uranus, that is, in the language of the Greeks, Heaven.

Piazzi, scanning the zodiac from his observatory in Palermo, in the early hours of that first night of the century, noticed a hitherto unobserved star, which under higher power proved to be a planet. It presented a small irregular disc, and a few additional observations showed that it was progressing in the usual manner from west to east. For some time such a revelation had been expected; but the result did not answer to expectation in one particular; for the new body seemed to be too insignificant to be called a world. It appeared rather to be a great planetary boulder, as if our Mount Shasta had been wrenched from the earth and flung into space. Investigation showed that the new body was more than a hundred miles in diameter; but this, according to planetary estimation, is only the measurement of a clod.

There had been, as we say, expectation of a discovery in the region where the first asteroid was found. Kepler had declared his belief that in this region of space a new world might be discovered. Following this suggestion, the German astronomer Olbers, of Bremen, had formed an association of twenty-four observers in different parts of Europe, who should divide among themselves the zodiacal band, and begin a system of independent scrutiny, either to verify or disprove Kepler's hypothesis.

There was another reason also of no small influence tending to the same end. Johann Elert Bode, another German astronomer, born in 1747 and living to 1826, had propounded a mathematical formula known as Bode's Law, which led those who accepted it to the belief that a planet would be found in what is now known as the asteroidal space. Bode's Law, so-called, seems to be no real law of planetary distribution; and yet the coincidences which are found under the application of the law are such as to arouse our interest if not to produce a conviction of the truth of the principle involved. Here, then, is the mathematical formula, which is known as Bode's Law:

Write from left to right a row of 4's and under these, beginning with the second 4, place a geometrical series beginning with 3 and increasing by the ratio of 2; add the two columns together, and we have a series running 4, 7, 10, etc.; and this row of results has an astonishing coincidence, or approximate coincidence with the relative distances of the planets from the sun—thus:

The near agreement of this row of results with the row containing the actual relative distances of the planets from the sun may well astonish, not only the astronomer, but the common reader. Those distances—making 10 to represent the distance of the earth—are as follows:

Mercury, 3.9; Venus, 7.2; Earth, 10; Mars, 15.2; Asteroids, 27.4; Jupiter, 52; Saturn, 95.4; Uranus, 192; Neptune, 300.

In addition to Kepler's prediction and the indications of Bode's Law, there was a general reason for thinking that a planetary body of some kind should occupy the space between the orbits of Mars and Jupiter. The mean distance of Mars from the sun is about 141,500,000 miles; that of Jupiter, is about 483,000,000 miles. The distance from one orbit to the other is therefore about 341,500,000 miles. Conceive of an infinite sheet of tin. Mark thereon a centre for the sun. Measure out a hundred and forty millions of miles, and with that radius strike a circle. From the same centre measure out four hundred and eighty-three millions of miles, and with that radius strike a circle. Cut out the sheet between the two circles, and the vast space left void will indicate the vacant area in the mighty disc of our solar system. That this space should be occupied with something accords with the plan of nature and the skill of the Builder.

So Olbers and his twenty-three associates began, in the last decade of the eighteenth century, to search diligently for the verification of Kepler's prediction and the fulfillment of Bode's Law. Oddly enough, Piazzi was not one of the twenty-four astronomers who had agreed to find the new world. He was exploring the heavens on his own account, and in doing so, he found what the others had failed to find, that is, the first asteroid.

The body discovered answered so little to the hopes of the astronomical fraternity that they immediately said within themselves: "This is not he; we seek another." So they continued the search, and in a little more than a year Olbers himself was rewarded with the discovery of the second of the planetoid group. On the twenty-eighth of March, 1802, he made his discovery from an upper chamber of his dwelling in Bremen, where he had his telescope. On the night in question he was scanning the northern part of the constellation of Virgo, when the sought-for object was found. This body, like the first of its kind, was very small, and was found to be moving from west to east in nearly the same orbit as its predecessor.

Here then was something wonderful. Olbers at once advanced the hypothesis that probably the two bodies thus discovered were fragments of what had been a large planet moving in its orbit through this part of the heavens. If so there might be—and probably were—others of like kind. The search was at once renewed, and on the night of the first of September, 1804, the third of the asteroid group was found by the astronomer Hardy, of Bremen. The belief that a large planet had been disrupted in this region was strengthened, and astronomers continued their exploration; but two years and a half elapsed before another asteroid was found. On the evening of March 29, 1807, the diligence of Olbers was rewarded with the discovery of the fourth of the group, which like its predecessors, was so small and irregular in character as still further to favor the fragmentary theory.

How shall we name the asteroids? Piazzi fell back upon pagan mythology for the name of his little world, and called it Ceres, from the Roman goddess of corn. Olbers named the second asteroid Pallas; the third was called Juno—whose rank in the Greek and Roman pantheon might have suggested one of the major planets as her representative in the skies; and the fourth was called Vesta, from the Roman divinity of the hearthstone.

Here then there was a pause. Though the zodiac continued to be swept by many observers, a period of more than thirty-eight years went by before the fifth asteroid was found. The cycle of these discoveries strikingly illustrates the general movement of scientific progress. First there is a new departure; then a lull, and then a resumption of exploration and a finding more fertile than ever. It was on the night of the eighth of December, 1845, that the German astronomer Hencke discovered the fifth asteroid and named it Astræa. After a year and a half, namely, on the night of the first of July, 1847, the same observer discovered the sixth member of the group, and to this was given the name Hebe. On the thirteenth of August in the same year the astronomer Hind found the seventh asteroid, and named it Iris. On the eighteenth of October following he found the eighth, and this was called Flora. Then on the twenty-fifth of April, 1848, came the discovery of Metis, by Graham. Nearly a year later the Italian De Gasparis found the tenth member of the system, that is, Hygeia. De Gasparis soon discovered the eleventh body, which was called Parthenope. This was on the eleventh of May, 1850.

Two other asteroids were found in this year; and two in 1851. In the following year nine were discovered; and so on from year to year down to the present date. Some years have been fruitful in such finds, while others have been comparatively barren. In a number of the years, only a single asteroid has been added to the list; but in others whole groups have been found. Thus in 1861 twelve were discovered; in 1868, twelve; in 1875, seventeen; in 1890, fourteen. Not a single year since 1846 has passed without the addition of at least one known asteroid to the list.

But while the number has thus increased to an aggregate at the close of 1890 of three hundred and one, many of the tiny wanderers have escaped. Some have been rediscovered; and it is possible that some have been twice or even three times found and named. The whole family perhaps numbers not only hundreds, but thousands; and it can hardly be doubted that only the more conspicuous members of the group have ever yet been seen by mortal eye.

A considerable space about the centre of the planetary zone between Mars and Jupiter is occupied with these multitudinous pigmy worlds that follow the one the other in endless flight around the sun. It is a sort of planetary shower; and it can hardly be doubted that the bodies constituting the flight are graded down in size from larger to smaller and still smaller until the fragments are mere blocks and bits of world-dust floating in space. Possibly there may be enough of such matter to constitute a sort of planetary band that may illumine a little (as seen from a distance) the zone where it circulates.

As to the origin of this seemingly fragmentary matter, we know nothing, and conjectures are of little use in scientific exposition. It may be true that a large planet once occupied the asteroidal space, and that the same has been rent by some violence into thousands of fragments. It may be observed that the period of rotation of the inferior planets corresponds in general with that of our earth, while the corresponding period of the superior or outside planets is less than one-half as great. The forces which produced this difference in the period of rotation may have contended for the mastery in that part of our solar system where the asteroids are found; and the disruption may have resulted from such conflict of forces.

Or again, it may be that a large planet is now in process of formation in the asteroidal space. Possibly one of the greater fragments may gain in mass by attracting to itself the nearer fragments, and thus continue to wax until it shall have swept clean the whole pathway of the planetary matter, except such small fragments as may after æons of time continue to fall upon the master body, as our meteorites now at intervals rush into our atmosphere and sometimes reach the earth.

Some astronomers have given and are still giving their almost undivided attention to asteroidal investigation. The discoveries have been mostly made by a few principal explorers. The astronomer, Palisa, from the observatory of Pola and that of Vienna, has found no fewer than seventy-five of the whole group. The observer, Peters, at Clinton, New York, has found forty-eight asteroids; Luther, of Düsseldorf, twenty-four; Watson, of Ann Arbor, twenty-two; Borrelly, of Marseilles, fifteen; Goldschmidt, of Paris, fourteen, and Charlois, of Nice, fourteen. The English astronomers have found only a few. Among such, Hind of London, who has-discovered ten asteroids, is the leader.

The Italian, German and American astronomers are first in the interest and success which they have shown in this branch of sky-lore. Their investigations have made us acquainted with the dim group of little worlds performing their unknown part in the vast space between the Warrior planet and Jove.

THE STORY OF NEPTUNE.

The discovery of the planet Neptune by Dr. Galle on the twenty-third of September, 1846, was one of the most important events in the intellectual history of this century. Certainly it was no small thing to find a new world. Discoverers on the surface of our globe are immortalized by finding new lands in unknown regions. What, therefore, should be the fame of him who finds a new world in the depths of space? Perhaps the discoverer of an asteroid or planetary moon may not claim, in the present advanced stage of human knowledge, to rank among the flying evangels of history; but he who found the great planet third in rank among the worlds of the solar system, a world having a mass nearly seventeen times as great as that of our own, may well be regarded as one of the immortals.

We have referred the discovery of Neptune to Dr. Johann Gottfried Galle, the German astronomer and Professor of Natural Sciences at Berlin. But this Dr. Galle was only the eye with which the discovery was made. He was a good eye; but the eye, however clear, is only an organ of something greater than the eye, and that something in this case consisted of two parts. The first part was Urbain Jean Joseph Leverrier, the French astronomer, of the Paris Observatory. The other part was Professor John Couch Adams, the astronomer of the University at Cambridge, England. These two were the thinkers; that is, they were, as it were, jointly the great mind of the age, of which Galle was the eye.

In getting a clear notion of the discovery of Neptune, several other personages are to be considered. One of these is the astronomer Alexis Bouvart, of France, who was born in Haute Savoie, in 1767, and died in June of 1843, three years before Neptune was found. Another personage was his nephew, the astronomer E. Bouvart, and a third was the noted Prussian, Friedrich Wilhelm Bessel, Director of the Observatory at Königsberg, who was born in 1784, and died on the seventeenth of March, 1846, only six months before the discovery of our outer planet.

Still another character to be commemorated is the English astronomer Professor James Challis, Plumian Professor and Director of the Observatory at Cambridge, England. This contributor to the great event was born in 1803, and died at Cambridge on the third of December, 1882. Still another, not to be disregarded, is Dr. T.J. Hussey, of Hayes, England, whose mind seems to have been one of the first to anticipate the existence of an ultra-Uranian planet. And still again, the English astronomer royal, Sir G.B. Airy must be mentioned as a contributor to the final result; but he is to be regarded rather as a contributor by negation. The great actors in the thing done were Leverrier, Adams and Galle. English authors contend strongly for placing the names in this order: Adams, Leverrier and Galle.

Suffice it to say that when Uranus was discovered by the elder Herschel in 1781, that world was supposed to be the outside planet of our system. Hitherto the splendid Saturn had marked the uttermost excursion of astronomical knowledge as it respected our solar group. For about a quarter of a century after Herschel's discovery the world rested upon it as a finality. The orbit of Uranus was thought to circumscribe the whole. But in the meantime, observations of this orbit led to the knowledge that it did not conform in all respects to astronomical and mathematical conditions. The orbit showed irregularities, disturbances, perturbations, that could not be accounted for when all of the known mathematical calculations were applied thereto. Uranus was seen to get out of his path. At times he would lag a little, and then at other times appear to be accelerated. Each year, when the earth would swing around on the Uranian side of the sun, the observations were renewed, but always with the result that the planet did not seem to conform perfectly to the conditions of his orbit. What could be the cause of this seeming disregard of mathematical laws?

Astronomers could not accept the supposition that there was any actual violation of the known conditions of gravitation. Certainly Uranus was following his orbit under the centripetal and centrifugal laws in the same manner as the other planets. There must, therefore, be some undiscovered disturbing cause. It had already been noted that in the case of the infra-Uranian planets they were swayed somewhat from their paths by the mutual influence of one upon the other. This was noticeable in particular in the movements of Jupiter, Saturn and Uranus. When Saturn, for instance, would be on the same side of the sun with Jupiter, it might be noted that the latter was drawn outward and the former inward from their prescribed curves. The perturbation was greatest when the planets were nearest, together. In like manner Uranus did obeisance to both his huge neighbors on the sun's side of his orbit. He, too, veered toward them as he passed, and they in turn recognized the courtesy by going out of their orbits as they passed. What, therefore, should be said of the outswinging movement of Uranus from his orbit in that part of his course where no disturbing influence was known to exist? Certainly something must be in that quarter of space to occasion the perturbation. What was it?

It would appear that the elder Bouvart, the French astronomer referred to above, was the first to suggest that the disturbances in the orbit of Uranus, throwing that planet from his pathway outward, might be and probably were to be explained by the presence in outer space of an unknown ultra-Uranian planet. Bouvart prepared tables to show the perturbations in question, and declared his opinion that they were caused by an unknown planet beyond. No observer, however, undertook to verify this suggestion or to disprove it. Nor did Bouvart go so far as to indicate the particular part of the heavens which should be explored in order to find the undiscovered world. His tables, however, do show from the perturbations of the orbits of Jupiter, Saturn and Uranus that the same are caused by the mutual influence of the planets upon one another.

It seems to have remained for Dr. T.J. Hussey, of Hayes, England, to suggest the actual discovery of the unknown planet by following the clew of the disturbance produced by its presence in a certain field of space. Dr. Hussey, in 1834, wrote to Sir George Biddell Airy, astronomer royal at Greenwich, suggesting that the perturbation of the orbit of Uranus might be used as the clew for the discovery of the planet beyond. But Sir George was one of those safe, conservative scholars who scorn to follow the suggestions of genius, preferring rather to explore only what is known already. He said in answer that he doubted if the irregularity in the Uranian orbit was in such a state of demonstration as to give any hope of the discovery of the disturbing cause. He doubted even that there was such irregularity in the Uranian orbit. He was of opinion that the observers had been mistaken in the alleged detection of perturbations. So the Greenwich observatory was not used on the line of exploration suggested by Hussey.

Three years afterward, and again in 1842, Sir George received letters from the younger Bouvart, again suggesting the possibility and probability of discovering the ultra-Uranian planet. These hints were strengthened by a letter from Bessel, of Königsberg. But Sir George B. Airy refused to be led in the direction of so great a possibility.

It was in 1844 that Professor James Challis, of the Cambridge observatory, appealed to Sir George for the privilege of using or examining the recorded observations made at Greenwich of the movements of Uranus, saying that he wished these tables for a young friend of his, Mr. John C. Adams, of Cambridge, who had but recently taken his degree in mathematics. Adams was at that date only twenty-five years of age. The royal astronomer granted the request, and for about a year Adams was engaged in making his calculations. These were completed, and in September of 1845, Challis informed Sir George Airy that according to the calculations of Adams the perturbations of Uranus were due to the influence of an unknown planet beyond.

The young mathematician indicated in his conclusions at what point in the heavens the ultra-Uranian world was then traveling, and where it might be found. But even these mathematical demonstrations did not suffice to influence Sir George in his opinions. He was an Englishman! He refused or neglected to take the necessary steps either to verify or to disprove the conclusions of Adams. He held in hand the mathematical computations of that genius from October of 1845 to June of the following year, when the astronomer Leverrier, of Paris, published to the world his own tables of computation, proving that the disturbances in the orbit of Uranus were due to the influence of a planet beyond, and indicating the place where it might be found. There was a close agreement between the point indicated by him and that already designated by Adams.

It seems that this French publication at last aroused Sir George Airy, who now admitted that the calculations of Adams might be correct in form and deduction. He accordingly sent word to Professor Challis to begin a search for the unknown orb. The latter did begin the work of exploration, and presently saw the planet. But he failed to recognize it! There it was; but the observer passed it over as a fixed star. As for Leverrier, he sent his calculations to Dr. Galle, of Berlin; and that great observer began his search. On the night of the twenty-third of September, 1846, he not only saw but caught the far-off world. There it was, disc and all; and a few additional observations confirmed the discovery.

Hereupon Sir George Airy broke out with a claim that the discovery belonged to Adams. He was able to show that Adams had anticipated Leverrier by a few months in his calculations; but the French scholars were able to carry the day by showing that Adams' work had been void of results. The world went with the French claim. Adams was left to enjoy the fame of merit among the learned classes, but the great public fixed upon Leverrier as the genius who did the work, and Dr. Galle as his eye.

Several remarkable things followed in the train. It was soon discovered that both Leverrier and Adams had been favored by chance in indicating the field of space where Uranus was found. They had both proceeded upon the principle expressed in Bode's Law. This law indicated the place of Neptune as 38.8 times the distance of the earth from the sun. A verification of the result showed that the new-found planet was actually only thirty times as far as the earth from the sun. In the case of all the other planets, their distances had been remarkably co-incident with the results reached by Bode's Law; but Uranus seemed to break that law, or at least to bend it to the point of breaking—a result which has never to this day been explained.

It chanced, however, that at the time when the predictions of Leverrier and Adams were sent, the one sent to Galle and the other to Challis, Uranus and the earth and the sun were in such relations that the departure of the orbit of Uranus from the place indicated by Bode's Law did not seriously displace the planet from the position which it should theoretically occupy. Thus, after a little searching, Challis found the new world, and knew it not; Galle found it and knew it, and tethered it to the planetary system, making it fast in the recorded knowledge of mankind.

While Daniel O'Connell, the greatest Irishman of the present century, despairing of the cause of his country, lay dying in Genoa, and while Zachary Taylor, at the head of a handful of American soldiers was cooping up the Mexican army in the old town of Monterey, a new world, 37,000 miles in diameter and seventeen times as great in mass as the little world on which we dwell, was found slowly and sublimely making its way around the well nigh inconceivable periphery of the solar system!

EVOLUTION OF THE TELESCOPE.

The development of telescopic power within the present century is one of the most striking examples of intellectual progress and mastery in the history of mankind. The first day of the century found us, not, indeed, where we were left by Galileo and Copernicus in the knowledge of the skies and in our ability to penetrate their depths, but it did find us advanced by only moderate stages from the sky-lore of the past.

The after half of the eighteenth century presents a history of astronomical investigation and deduction which confirmed and amplified the preceding knowledge; but that period did not greatly widen the field of observation. If the sphere of space which had been explored on the first day of January, 1801, could be compared with that which is now known and explored by our astronomers, the one sphere would be to the other even as an apple to the earth.

It is difficult to apprehend the tremendous strides which we have made in the production of telescopes and the consequent increase in our sweep of the heavens. It was only in 1774 that the elder Herschel began his work in the construction of reflecting telescopes. These he gradually increased in size, until near the close of the century, when he produced an instrument which magnified two hundred and twenty-seven diameters. In the course of his career he built two hundred telescopes, having a seven-foot focus; 150 of ten feet and about eighty of twenty feet each.

With these instruments the astronomical work in the last quarter of the eighteenth century was mostly performed. The study of the heavens at this epoch began to reach out from the planetary system to the fixed stars. In this work Herschel led the way. The planet Uranus at first bore the name of Herschel, from its discoverer. Sir John Herschel, son of Sir William, was born in 1792. All of his astronomical work was accomplished in our century. Following the line of his father, he used the reflecting telescope, and it was an instrument of this kind that he took to his observatory at the Cape of Good Hope. Lord Rosse was born in the year 1800. Under his auspices the reflecting telescope reached its maximum of power and usefulness. His great reflector, built in his own grounds at Birr Castle, Ireland, was finished in 1844. This instrument was the marvel of that epoch. It had a focal distance of fifty-three feet, and an aperture of six feet. With this great telescope its master reached out into the region of the nebulæ, and began the real work of exploring the sidereal heavens.

In the reflecting telescope, however, there are necessary limitations. Before the middle of this century, it was known that the future of astronomy depended upon the refracting lens, and not on the speculum. The latter, in the hands of the two Herschels and Rosse, had reached its utmost limits—as is shown by the fact that to this day the Rosse telescope is the largest of its kind in the world.

Meanwhile the production of refracting telescopes made but slow progress. As late as 1836 the largest instrument of this kind in the world was the eleven-inch telescope of the observatory at Munich. The next in importance was a nine and a half-inch instrument at Dorpat, in Russia. This was the telescope through which the astronomer Struve made his earlier studies and discoveries. His field of observation was for the most part the fixed and double stars. At this time the largest instrument in the United States was the five-inch refractor of Yale College. Soon afterward, namely, in 1840, the observatory at Philadelphia was supplied with a six-inch refracting telescope from Munich.

German makers were now in the lead, and it was not long until a Munich instrument having a lens of eleven inches diameter was imported for the Mitchell Observatory on Mount Adams, overlooking Cincinnati. About the same time a similar instrument of nine and a half inches aperture was imported for the National Observatory at Washington. To this period also belongs the construction of the Cambridge Observatory, with its fifteen-inch refracting telescope. Another of the same size was produced for the Royal Observatory at Pulkova, Russia. This was in 1839; and that instrument and the telescope at Cambridge were then the largest of their kind in the world.

The history of the telescope-making in America properly begins with Alvan Clark, Sr., of Cambridgeport, Massachusetts. It was in 1846 that he produced his first telescope. Of this he made the lens, and such was the excellence of his work that he soon became famous, to the degree that the importation of foreign telescopes virtually ceased in the United States. Nor was it long until foreign orders began to arrive for the refracting lenses of Alvan Clark & Sons. The fame of this firm went out through all the world, and by the beginning of the last quarter of the century the Clark instruments were regarded as the finest ever produced.

We cannot here refer to more than a few of the principal products of Clark & Sons. Gradually they extended the width of their lenses, gaining with each increase of diameter a rapidly increasing power of penetration. At last they produced for the Royal Observatory of Pulkova a twenty-seven-inch objective, which was, down to the early eighties, the master work of its kind in the world. It was in the grinding and polishing of their lenses that the Clarks surpassed all men. In the production of the glass castings for the lenses, the French have remained the masters. At the glass foundry of Mantois, of Paris, the finest and largest discs ever produced in the world are cast. But after the castings are made they are sent to America, to be made into those wonderful objectives which constitute the glory of the apparatus upon which the New Astronomy relies for its achievements.

It was in the year 1887 that the Lick Observatory on Mount Hamilton, of the Coast Range in Southern California, was completed. The lens of this instrument is thirty-six inches in diameter. Nor will the reader without reflection readily realize the enormous stride which was made in telescopy when the makers advanced from the twenty-seven-inch to the thirty-six-inch objective. Lenses are to each other in their power of collecting light and penetrating apace as the squares of their diameters, and in the extent of space explored as the cubes of their diameters.

The objective of the Pulkova instrument is to that of the Lick Observatory as 3 is to 4. The squares are as 9 is to 16, and the cubes are as 27 is to 64. This signifies that the depth of space penetrated by the Lick instrument is to that of its predecessor as 16 is to 9, and that the astronomical sphere resolved by the former is to the sphere resolved by the latter as 64 is to 27—that is, the Lick instrument at one bound revealed a universe more than twice as great as all that was known before! The human mind at this one bound found opportunity to explore and to know a sidereal sphere more than twice as extensive as had ever been previously penetrated by the gaze of man.

Nor is this all. The ambition of American astronomers and American philanthropists has not been content with even the prodigious achievement of the Lick telescope. In recent years an observatory has been projected in connection with the University of Chicago, which has come almost to completion, and which will bear by far the largest telescopic instrument in the world. The site selected for the observatory is seventy-five miles from the city, on the northern shore of Lake Geneva. There is a high ground here, rising sufficiently into a clear atmosphere, nearly two hundred feet above the level of the lake.

The observatory and the great telescope which constitutes its central fact are to bear the name of the donor, Mr. Yerkes, of Chicago, who has contributed the means for rearing this magnificent adjunct of the University. The enterprise contemplated from the first the construction of the most powerful telescope ever known. The manufacture of the objective, upon which everything depends, was assigned to Mr. Alvan G. Clark, of Cambridgeport, Massachusetts, who is the only living representative of the old firm of Alvan Clark & Sons.

Alvan G. Clark has inherited much of the genius of his father, though it is said that in making the lens of the Lick Observatory the father had to be called from his retirement to superintend personally some of the more delicate parts of the finishing before which task his sons had quailed. But the younger Clark readily agreed to make the Geneva lens, under the order of Yerkes, and to produce a perfect objective forty inches in diameter! This important work, so critical—almost impossible—has been successfully accomplished.

The making and the mounting of the Yerkes telescope have been assigned to Warner & Swasey, of Cleveland, Ohio, who are recognized as the best telescope builders in America. The great observatory is approaching completion. The instrument itself has been finished, examined, accepted by a committee of experts, and declared to fulfill all of the conditions of the agreement between the founder and the makers. Thus, just north of the boundary line between Illinois and Wisconsin, the greatest telescope of the world has been lifted to its dome and pointed to the heavens.

The formal opening of the observatory is promised for the summer months of 1896. The human mind by this agency has made another stride into the depths of infinite space. Another universe is presently to be penetrated and revealed. A hollow sphere of space outside of the sphere already known is to be added to the already unthinkable universe which we inhabit. Every part of the immense observatory and of the telescope is of American production, with the single important exception of the cast glass disc from which the two principal lenses, the one double convex and the other plano-concave, are produced. These were cast by Mantois, of Paris, whose superiority to the American manufacturers of optical glass is recognized.

It is estimated that the Yerkes telescope will gather three times as much light as the twenty-three-inch instrument of the Princeton Observatory. It surpasses in the same respect the twenty-six-inch telescope at the National Observatory in the ratio of two and three-eighths to one. It is in the same particular one and four-fifth times as powerful as the instrument of the Royal Russian Observatory at Pulkova; and it surpasses the great Lick instrument by twenty-three per cent.

What the practical results of the study of the skies through this monster instrument will be none may predict. Theoretically it is capable of bringing the moon to an apparent distance of sixty miles. Under favorable circumstances the observer will be able to note the characteristics of the lunar landscape with more distinctness than a good natural eye can discern the outlines and character of the summit of Pike's Peak from Denver. The instrument has sufficient power to reveal on the lunar disc any object five hundred feet square. Such a thing as a village or even a great single building would be plainly discernible.

Professor C.A. Young has recently pointed out the fact that the Yerkes telescope, if it meets expectation, will show on the moon's surface with much distinctness any such object as the Capitol at Washington. It is complained that in America wealth is selfish and self-centred; that the millionaire cares only for himself and the increase of his already exorbitant estate. The ambition of such men as Lick of San Jose and Yerkes of Chicago, seems to ameliorate the severe judgment of mankind respecting the holders of the wealth of the world, and even to transform them from their popular character of enemies and misers into philanthropists and benefactors.

THE NEW ASTRONOMY.

This century has been conspicuous above all centuries for new things. Man has grown into new relations with both nature and thought. He has interpreted nearly everything into new phraseology and new forms of belief. The scientific world has been revolutionized. Nothing remains in its old expression. Chemistry has been phrased anew. The laws of heat, light and electricity have been either revised or discovered wholly out of the unknown. The concept of universal nature has been so translated and reborn that a philosopher coming again out of the eighteenth century would fail to understand the thought and speech of even the common man.

In no other particular has the change been more marked than with respect to the general theory of the planetary and stellar worlds. A New Astronomy has come and taken the place of the old. The very rudiments of the science have to be learned as it were in a new language, and under the laws and theories of a new philosophy. Nature is considered from other points of view, and the general course of nature is conceived in a manner wholly different from the beliefs of the past.

In a preceding study we have explained the general notion of planetary formation according to the views of the last century. The New Astronomy presents another theory. Beginning with virtually the same notion of the original condition of our world and sun cluster, the new view departs widely as to the processes by which the planets were formed, and extends much further with respect to the first condition and ultimate destiny of our earth. The New Astronomy, like the old, begins with a nebular hypothesis. It imagines the matter now composing the solar group to have been originally dispersed through the space occupied by our system, and to have been in a state of attenuation under the influence of high heat. Out of this condition of diffusion the solar system has been evolved. The idea is a creation by the process of evolution; it is evolution applied to the planets. More particularly, the hypothesis is that the worlds of our planetary system grew into their present state through a series of stages and slow developments extending over æons of time.

This is the notion of world-growth substituted for that of world-production en masse by the action of centrifugal force and discharge from the solar equator. The New Astronomy proposes in this respect two points of remarkable difference from the view formerly entertained. The first relates to the fixing of the planetary orbits, and the other to the process by which the planets have reached their present mass and character. The old theory would place a given world in its pathway around the sun by a spiral flinging off from the central body, and would allow that the aggregate mass of the globe so produced was fixed once for all at the beginning. The new theory supposes that a given planetary orbit, as for instance that of the earth, was marked in the nebula of our system before the system existed—that is, that our orbit had its place in the beginning just as it has now; that the orbit was not determined by solar revolution and centrifugal action, but that it was mathematically existent in the nebular sheet out of which the solar system was produced.

Other lines existed in the same sheet of matter. One of these lines or pathways was destined for the orbit of Mercury; another for the orbit of Venus. One was for the pathway of Mars; another for the belt of the asteroids; another for Jupiter; another for Saturn, and still two others, far off on the rim, for Uranus and Neptune. The theory continues that such are the laws of matter that these orbital lines must exist in a disc of fire mist such as that out of which our solar universe has been produced. The New Astronomy holds firmly to the notion that the orbits of the planets are as much a part of the system as the planets themselves, and that both orbit and planet exist in virtue of the deep-down mathematical formulæ on which the whole material universe is constructed.

Secondly, the New Astronomy differs from the old by a whole horizon in the notion of world-production. About the middle of the century the theory began to be advanced that the worlds grew by accretion of matter; that they grew in the very paths which they now occupy; that they began to be with a small aggregation of matter rushing together in the line or orbit which the coming planet was to pursue. The planetary matter was already revolving in this orbit and in the surrounding spaces. It was already floating along in a nebulous superheated form capable of condensation by the loss of heat, but in particular capable of growth and development by the fall of surrounding matter upon the forming globe. We must remember that in the primordial state the elements of a planet, as for instance our earth, were mixed together and held in a state of tenuity ranging all the way from solid to highly vaporized forms, and that these elements subsequently and by slow adjustment got themselves into something approximating their present state.

The New Astronomy contemplates a period when each of the planets was a germinal nucleus of matter around which other matter was precipitated, thus producing a kind of world-growth or accretion. Thus, for instance, our earth may be considered at a time when its entire mass would not, according to our measurement, have weighed a hundred pounds! It consisted of a nucleus around which extended, through a great space, a mass of attenuated planetary matter. The nucleus once formed the matter adjacent would precipitate itself by gravitation upon the surface of the incipient world. The precipitation would proceed as heat was given off into space. It was virtually a process of condensation; but the result appeared like growth.

To the senses a planet would seem to be forming itself by accretion; and so, indeed, in one sense it was; for the mass constantly increased. As the nucleus sped on in the prescribed pathway, it drew to itself the surrounding matter, leaving behind it an open channel. The orbit was thus cleared of the matter, which was at first merely nebular, and afterward both nebular and fragmentary. The growth at the first was rapid. With each revolution a larger band of space was swept clear of its material. With each passage of the forming globe the matter from the adjacent spaces would rush down upon its surface, and as the mass of the planet increased the process would be stimulated; for gravitation is proportional to the mass. At length a great tubular space would be formed, having the orbit of the earth for its centre, and in this space the matter was all swept up. The tube enlarged with each revolution, until an open way was cut through the nebular disc, and then from the one side toward Venus and from the other side toward Mars the space widened and widened, until the globe took approximately by growth its present mass of matter. The nebulous material was drawn out of the inter-planetary space where it was floating, and the shower of star dust on the surface of the earth became thinner and less frequent. In some parts of the orbit bands or patches of this material existed, and the earth in passing through such hands drew down upon itself the flying fragments of such matter as it continues to do to the present day. What are meteoric displays but the residue of the primordial showers by which the world was formed?

All this work, according to the New Astronomy, took place while our globe was still in a superheated condition. The mass of it had not yet settled into permanent form. The water had not yet become water; it was steam. The metals had not yet become metals; they were rather the vapor of metals. At length they were the liquids of metals, and at last the solids. So, also, the rocks were transformed from the vaporous through the liquid into the solid form—all this while the globe was in process of condensation. It grew smaller in mathematical measurements at the same time that it grew heavier by the accretion of matter. At last the surface was formed, and in time that surface was sufficiently cooled to allow the vapors around it to condense into seas and oceans and rivers. There were ages of superficial softness—vast epochs of mud—in which the living beings that had now appeared wallowed and sprawled.

We cannot trace the world-growth through all its stages but can only indicate them as it were in a sketch. The more important thing to be noted is the relation of our planet in process of formation to the great fact called life. Here the New Astronomy comes in again to indicate, theoretically at least, the philosophy of planetary evolution. Each planet seems to pass through a vast almost inconceivable period in which its condition renders life on its surface or in its structure impossible. Heat is at once the favoring and the prohibitory condition of life. Without heat life cannot exist; with too great heat life cannot exist. With an intermediate and moderate degree of heat many forms of animate and inanimate existence may be promoted.

These facts tend to show that every world has in its career an intermediate period which may be called the epoch of life. Before the epoch of life begins there is in the given world no such form of existence. There is matter only. Then at a certain stage the epoch of life begins. The epoch of life continues for a vast indeterminate period. No doubt in some of the worlds an epoch of life has been provided ten times as great, possibly a thousand times as great, as in other planets. After the epoch of life begins only certain forms of existence are for a while possible. Then other and higher forms succeed them, and then still higher. Thus the process continues until the highest—that is, the conscious and moral form of existence becomes possible, and that highest, that conscious, that moral form of being is ourselves.

This is not all. The epoch of life seems to be terminable at the further extreme by a planetary condition in which life is no longer possible. The New Astronomy indicates the coming of a condition in all the worlds when life must disappear therefrom and be succeeded by a lifeless state of worldhood. This may be called the epoch of death—that is, of world-death. It seems to be almost established by investigation and right reason that worlds die. They reach a stage in which they are lifeless. They cool down until the waters and gases that are on the surface and above the surface recede more and more into the surface and then into the interior, until they wholly disappear. Cold takes the throne of nature. Universal aridity supervenes, and all forms of vegetable and animate existence go away to return no more. They dwindle and expire. The conditions that have come are virtually conditions of death.

Whether the universe contains within itself, under the Almighty supervision, certain arrangements and laws by which the dead world can be again cast into the crucible and regenerated by liberation through the action of heat into its primordial state once more and go the same tremendous round of planet life, we know not. The conception of such a process, even the dream or vague possibility of it, is sufficiently sublime and fills the mind with a great delight in contemplating the possible cycles through which the material universe is passing.

At any rate, we may contemplate the three great stages of world-life with which we are already acquainted—that is, the birth stage, the epoch of life and the epoch of death. There is a birth, as also a life and a death of planets. Richard A. Proctor, of great fame, on one of his last tours of instructive lecturing among our people, had for his subject the "Birth and Death of Worlds." The theme was not dissimilar to that which has been here presented in outline. The birth, the life and the death of worlds! Such is a summary of that almost infinite history through which our earth is passing—the history which the globe is making on its way from its nebulous to its final state.

Such, if we mistake not, is the story epitomized—the life history in brief—of all the worlds of space. They have each in its order and kind, an epoch of the beginning, then an epoch of growth and evolution, then an epoch of life—toward which all the preceding planet history seems to tend—and finally an epoch of death which must, in the course of infinite time, swallow from sight each planet in its turn, or at least reduce each from that condition in which it is an arena of animated existence into that state where it is a frozen and desert clod, still following its wonted path through space, still shining with a cold but cheerful face, like our moon, upon the silent abysses of the universe.

WHAT THE WORLDS ARE MADE OF.

The present century was already well advanced before there was any solid ground for the belief that the worlds of space are made of analogous or identical materials. It was only with the invention of the spectroscope and the analysis of light that the material identity of universal nature was proved by methods which could not be doubted. The proof came by the spectroscope.

This little instrument, though not famed as is its lordly kinsman the telescope, or even regarded with the popular favor of the microscope, has nevertheless carried us as far, and, we were about to say, taught us as much, as either of the others. It is one thing to see the worlds afar, to note them visibly, to describe their outlines, to measure their mass and determine their motions. It is another thing to know their constitution, the substances of which they are composed, the material condition in which they exist and the state of their progress in worldhood. The latter work is the task of the spectroscope; and right well has it accomplished its mission.

The solar spectrum has been known from the earliest ages. When the sun-bow was set on the background of cloud over the diluvial floods, the living beings of that age saw a spectrum—the glorious spectrum of rain and shine. Wherever the rays of light have been diffracted under given conditions by the agency of water drops, prism of glass or other such transparent medium, and the ray has fallen on a suitable screen, lo! there has been the beautiful spectrum of light.

The artificial, intentional production of this phenomenon of light has long been known, and both novice and scientist have tested and improved the methods of getting given results. The child's soap-bubble shows it in miniature splendor. The pressure of one wet pane of glass against another reveals it. The breakage of nearly all crystalline substances brings something of the colored effects of light; but the triangular prism of glass, suitably prepared, best of all displays the analysis of the sun-beam into the colors of which it is composed.

The spectroscope is the improved instrument by which the diffracting prism is best employed in producing the spectrum. The reader no doubt has seen a spectroscope, and has observed its beautiful work. In this place we pass, however, from the instrument of production to the spectrum, or analyzed result, as the same is shown on a screen. There the pencil of white light falling from the sun is spread out in the manner of a fan, presenting on the screen the following arrangement of colors: red, orange, yellow, green, blue, indigo and violet.

This order of colors, beginning with red, starts from that side of the spectrum which is least bent from the right line in which the white ray was traveling. The violet rays are most bent. The red rays are thus said to be at the lower edge of the prism, and the violet rays at the upper edge. Below the red rays there are now known to be certain invisible rays, as of heat and electricity. Above the violet rays are other invisible rays, such as the actinic influence. In fact, the spectrum, beginning invisibly, passes by way of the visible rays to the invisible again. Nor can any scientist in the world say at the present time how much is really included in the spread-out fan of analyzed sunlight.

Thus much scientists have known for some time. Certain other facts, however, in connection with the solar spectrum are of greater importance than are its more sensible phenomena. It was in the year 1802 that the English physicist, William Hyde Wollaston, discovered that the solar spectrum is crossed with a large number of dark lines. He it was who first mapped these lines and showed their relative position. He it was also who discovered the existence of invisible rays above the violet. Twelve years afterward Joseph von Fraunhofer, of Munich, a German optician of remarkable talents, took up the examination of the Wollaston lines, and by his success in the investigation succeeded in attracting the attention of the world.

This second stage in scientific discovery is generally that which receives the plaudits of mankind. It was so in the case of Fraunhofer. His name was given to the dark lines in the solar spectrum, and the nomenclature is retained to the present time. They are called the "Fraunhofer lines." It was soon discovered that the lines in question as produced in the spectrum are due to the presence of gases in the producing flame or source of light. It was also discovered that each substance in, the process of combustion yields its own line or set of lines. These appear at regular intervals in the spectrum. When several substances are consumed at the same time; the lines of each appear in the spectrum. The result is a system of lines, becoming more and more complex as the number of elements in the consuming materials is increased.

The lines in a narrow spectrum fall so closely together that they cannot be critically examined; but when more than one prism is used and the spectrum by this means spread out widely, the dark lines are made to stand apart. They are then found to number many thousands. We speak now of the analysis of sunlight. Experimentation was naturally turned, however, to terrestrial gases and solids on fire, and it was found that these also produce like series of dark lines in the spectrum. Or when the substances are consumed as solids, then the spectral effects are reversed, and the lines that would be dark lines in the luminous colored spectrum become themselves luminous lines on the screen; but these lines hold the same relation in mathematical measurement, etc., as do the dark lines in the colored spectrum.

Skillful spectroscopists succeeded in detecting and delineating the lines that were peculiar to each substance. By burning such substances in flame, they were able to produce the lines, and thus verify results. By such experimentation the various lines present in the solar spectrum were separated from the complex result, and the conclusion was reached that in the burning surface of the sun certain substances well known on earth are present; for the lines of those substances are shown in the spectrum.

No other known substances would produce the given lines. The conclusion is overwhelming that the substances in question are present in a gaseous condition in the burning flames of the sun. Down to the present time the examination of the sun's atmosphere has shown the existence therein of thirty-six known elements. These include sodium, potassium, calcium, magnesium, iron, copper, cobalt, silver, lead, tin, zinc, titanium, aluminium, chromium, silicon, carbon, hydrogen and several others.

It was thus established that in the constitution of the sun many of the well-known elements of the earth are present. There could be no mistake about it. An identity of lines in such a case proved beyond dispute the identity of the substance from which such lines are derived. The existence of common materials in the central sphere of our system and in one of his attendant orbs—our own—could not be doubted. The discovery of such a fact led by immediate inference to the expectation and belief that the other planets were of like constitution, or in a word, that the whole solar system was essentially composed of identical materials.

As the inquiry proceeded, it was found, however, that the agreement in the lines of different spectra was not perfect. Lines would be found in the spectrum derived from one source that were not present in a spectrum derived from another source. Materials were therefore suggested as present in one body that were not present in another. Still further inquiry confirmed the belief that while there is a general uniformity in the materials of our solar system, the identity is not complete in all. An element is found in one part that may not be found in another. Hydrogen shows its line in the spectrum derived from every heavenly body that has been investigated; but not so aluminium or cobalt. Sodium, that is, the salt-producing base, is discovered everywhere, but not nickel or arsenium. The result, in a word, shows a certain variability in the distribution of solar and planetary matter, but a general identity of most.

The question next presented itself as to the character of the luminous bodies beyond the solar system. Of what kind of matter are the comets? Of what kind are the fixed stars? Of what kind are the nebulæ? Could the spectroscope be used in determining also the character of the materials in those orbs that we see shining in the depths of space? The instrument was turned in answer to these questions to the sidereal heavens. No other branch of science has been prosecuted in the after half of this century with more zeal and success than has the spectroscopic analysis of the fixed stars. These are known by the telescope to have the character of suns. The most general fact of the visible heavens is the plentiful distribution of suns. They sparkle everywhere as the so-called fixed stars. To them the telescope has been virtually turned in vain. We say in vain because no single fixed star has, we believe, ever been made by aid of the telescope to show a disc.

On turning the telescope to a fixed star, its brightness, its brilliancy, increases according to the power of the instrument. Coming into the field of one of these great suns of space, the telescope shows a miraculous dawn spreading and blazing into a glorious sunrise, and a sun itself flaming like infinite majesty on the sight; but there is no disc—nothing but a blaze of glory. Thus in a sense the telescope has worked in vain on the visible heavens. But not so the spectroscope. The latter has done its glorious work. Turning to a given fixed star, it shows that the tremendous combustion going on therein is virtually the same as that in our own sun. There, too, is flaming hydrogen, and there is carbon and oxygen and iron and sodium and potassium and many other of the leading elements of what we thus know to be universal nature. The suns are all akin; they are cousins-german. They are of the same family—they and their progeny. They were born of the same universal fact. They are of the same Father! They are builded on the same plan, and they have a common destiny. Aye, more, the nebulæ that float far off, swanlike, in the infinitudes, are of the same family. The nebulæ may be regarded as the mothers of universes. It is out of their bosoms that the life and substance of all suns and worlds are drawn! And these, too, are composed of the common matter of universal nature. It is the same matter that we eat and drink. It is the same that we breathe. It is the same that we see aflame in our lamps and grates. It is the same that is borne to us in the fragrance of flowers planted on the graves of our dead. It is the common hydrogen and carbon and oxygen and nitrogen of our earth and its envelope. It is the soda of our bread; the potassa of our ashes; the phosphorus of our bones and brain! Indeed, the universe throughout is of one form and one substance, and there is one Father over all. Sooner or later the concepts of science and of religion will come together; and the small agitations and conflicts of human thought and hope will pass away in a sublime unity of human faith.