Front matter (continued 3)

In working these processes a thick plate of glass, after certain preliminary treatment, is coated with sensitized gelatin. The plate is then placed in a drying room or oven having a temperature of 120° F., baked until it is thoroughly dry, and allowed to cool gradually. The subject to be reproduced is then photographed in the usual manner, and unless a prism or mirror box has been used the negative is stripped and reversed in order to make the print reproduce the original in proper position. From the negative a contact print is made on the gelatin-coated plate, the parts or molecules of gelatin being hardened in proportion to the amount of light that affects them. After the contact print has been made the gelatin plate is thoroughly washed in cold water, in order to dissolve and wash out the bichromate and stop any further action of light on the plate, and is then thoroughly dried. Before prints are made from the gelatin-coated plate water is flowed on it and penetrates different parts of the gelatin according to their hardness. The darkest parts of the picture will correspond to the hardest and densest parts of the gelatin, which will not absorb water; the lighter parts will take up more water. The surface water is then removed with a rubber straight edge and an absorbent roller and the plate is ready for inking. The ink, being greasy, has no affinity for water, and when it is rolled over the plate it adheres only to the dry parts of the gelatin, and in the press is carried to the paper in all the lights and shades of the illustration. The plate is kept moist in printing.

The paper used for printing from photogelatin plates must be free from chemicals that will affect the gelatin. A nearly pure rag paper is generally used.

The photogelatin process is well adapted to the reproduction of paleontologic drawings, wash drawings, photographs, photomicrographs, works of art, old manuscripts—in fact, any kind of subject in which the reproduction of delicate lights and shades is essential. If properly manipulated it has distinct advantages over the half-tone process in that it can reproduce details and light and shade without showing the effect of a screen and without the use of coated paper. Excellent reproductions by the heliotype process are also made in color by first printing the design in a neutral tone and superposing appropriate transparent colors on this print, somewhat as in chromolithography, so that the colors softly blend with the shaded groundwork.

Reproductions made by the photogelatin process are more expensive than those made by the half-tone process, for the prints are generally made on better paper and are printed with greater care. They give no screen effect and are perhaps unrivaled by prints obtained by any other process except photogravure, in which the image is printed from a metal plate that has been sensitized, exposed under a reversed negative, and etched.

Changes can not be made on photogelatin plates except by making over the corrected parts. All retouching must be done on the originals or on the negatives made from then.

LITHOGRAPHY.

ORIGINAL PROCESS.

The general term "lithography" is sometimes used to indicate not only the original process so named, said to have been invented by Senefelder, but chromolithography, photolithography, and engraving on stone, as well as engraving on copper as a means of supplying matter to be transferred to and printed from a lithographic stone.

Senefelder discovered that limestone will absorb either grease or Water, and that neither one will penetrate a part of the surface previously affected by the other. He found that if a design is drawn on limestone with a greasy crayon and the stone afterward properly prepared with a solution of nitric acid and gum, greasy ink will adhere only to the parts that are covered with the crayon, and that the stone will give off an impression of the design.

Lithographic stone is described as a fine, compact, homogeneous limestone, which may be either a pure carbonate of lime or dolomitic—that is, it may contain magnesium. Although limestone is one of the most common rocks, limestone of a quality suitable for use in lithography is found at only a few localities.[11] There are two general classes of lithographic stone, known to the trade as "blue" or hard stone and "yellow" or soft stone. The blue stone is adapted for engraving and to the better grade of fine-line printing; the yellow stone is rated as somewhat inferior.

In the original process, which may here be termed plain lithography, two methods are employed in putting on stone the design to be reproduced. In one the subject or picture to be reproduced is drawn on the printing stone either with a lithographic crayon or with a pen dipped in lithographic ink or "tusche," which is oily or fatty, like the crayon. In the other method the drawing is made on transfer paper and transferred to the stone. In drawing on stone it is necessary to reverse the design, so that all lettering must be drawn backward. In doing this the artist often uses a mirror to aid him. If the drawing is made on transfer paper the design and the lettering are copied as in the original—not reversed.

Before a drawing is made on stone a stone of the quality suited to the particular design in hand is selected. The stone is then ground and polished, and if the drawing is to be made with crayon it is "grained" according to the special requirements of the subject. If the drawing is to be made with a pen and is to consist of "line work" the stone is polished. The first step is to obtain on the stone an outline or "faint" of the design. There are several ways to do this. By one method a tracing of the design is made, a sheet of thin paper covered with red chalk is laid face downward on the stone, the tracing is laid face downward over it, and the design is again traced in red-chalk lines on the stone. The method described is simple, but there are others that are more complicated and that are particularly applicable to the reproduction of photographs and other illustrations. Crayon work is often used in combination with pen and ink, stipple, and brush work. This method of drawing on stone is used also for preparing color stones in the process of chromolithography, in which there are many added details of manipulation. After the drawing has been made on the stone or transferred to it the stone is "gummed"—that is, it is covered with a solution of gum arabic and nitric acid—and dried. The stone is then dampened with water and carefully rolled with lithographic ink, which adheres to the pen or crayon work and is repelled elsewhere. It is then "rubbed" over with powdered rosin and talcum, which adheres to the ink and further protects the drawing from the effects of the etching fluid, which is next to be applied to the stone. This fluid consists of a 10 per cent solution of gum arabic to which 2 to 7 per cent of nitric acid has been added, the degree of acidity being varied according to the subject and the hardness of the stone. The fluid is applied with a brush or sponge and is left on the stone just long enough to decompose slightly the carbonate of lime on its surface and, after washing, to leave the design or drawing in very slight relief. The stone is again gummed and dried, and the design is "washed out" or brought out by removing the surface gum with a wet sponge and applying to the stone a rag sprinkled with turpentine and charged with printing ink. These operations wash away the tusche and the crayon that have been decomposed by the acid and expose the design faintly in white at first, but it gradually grows darker as it becomes charged with printing ink from the rag. The stone is next "rolled up" or inked. The slightly moistened surface repels the ink and the design takes it up, so that when the stone is run through the press the design is carried to the paper.

Lithographic prints from stones prepared in this way are made on a flat-bed press. The stone is carried forward to print and on its return is dampened and inked, an operation slower than that of rotary printing.

Corrections and changes are made on the stone by carefully scraping or polishing away the parts to be corrected and making the changes with a crayon or pen, but the design can not ordinarily be corrected twice in the same place, as the scraping or polishing removes a part of the surface of the stone and thus lessens the pressure at that place, and the impression there may be imperfect or may completely fail.

This form of lithography is seldom used for Survey illustrations but was formerly much used and is well adapted to the reproduction of drawings of fossils, particularly of remains of dinosaurs and other types of large extinct animals. Examples may be seen in Monographs 8 and 10 and in other early reports of the Geological Survey. The drawings for these illustrations were made directly on stone.

A drawing made on one stone may be transferred in duplicate or in any desired number to another stone, or to a properly grained sheet of zinc and aluminum, from which impressions may be printed on a lithographic press. Both these metals are also used for lithographic printing on rotary presses, the zinc or aluminum plate being bent and secured around a cylinder which rotates continuously in one direction. As one impression is made at each revolution of the cylinder the printing is rapid; but the best printing from a metal plate is inferior to the best printing from a lithographic stone.

PHOTOLITHOGRAPHY.

Photolithography, like other lithographic processes, has been improved greatly during the last few years—not particularly in results but in methods—by the introduction of metal plates, the rubber blanket offset, the Ben Day films, and many mechanical and chemical devices, so that a brief description of it will not explain the process except in a most general way. As photolithography is a direct process and is relatively cheap it is the one most used for reproducing large maps and other line drawings that have been carefully prepared. Zinc and aluminum plates are now much used in photolithography, for a direct contact photographic print can be made on them, they can be printed flat or bent for use on a rotary press, and they can be stored for future use more economically than stones.

There are two somewhat distinct methods of producing photolithographs. In both the ordinary photographic methods are used, but it is often necessary to "cut" or trace parts of the negative in order to open up lines and other features that are not sharp or well defined, so that the negative will print them sharp and clear. If the copy to be reproduced shows three colors, three negatives are made, one for each color, and the parts to be shown by each are preserved by "opaquing" or painting out all other parts. By the older method the negative thus perfected is placed in a printing frame in contact, under pressure, with sensitized transfer paper and is exposed to light. The printing frame is then carried to the dark room and the paper is removed from the frame and its surface covered with transfer ink. The paper is then laid face upward on water and soaked for several minutes, after which it is placed in the same position upon a slab of stone or metal and thoroughly washed with water. This washing removes the ink and the sensitive film from the parts that were unaffected by the action of light (the parts corresponding to the white paper in the design), but the ink still adheres to the lines of the design in the precise sharpness and clearness of the negative. The design is now ready to be transferred to the printing stone or zinc plate. The sheet is again slightly dampened between moist blotters and laid face downward in its correct position on a prepared stone or zinc plate, which is then pulled through a press under heavy pressure. The paper is then removed from the stone or plate, to which it has carried the design. From this point the gumming, etching, and other operations are practically the same as those used in ordinary lithography.

The bichromate-gelatin transfer process described above has been replaced in the Survey by a more satisfactory one, which insures absolute scale and reproduces the finest line drawings perfectly without thickening the lines or without distortion. In this process, which is known as the planographic process, a photographic negative of the "copy" is placed in a vacuum printing frame in contact with a zinc or aluminum plate that has been sensitized with a bichromate-albumen solution and exposed in front of an arc lamp. After proper exposure the plate is removed from the frame, inked over, and placed under water. The parts not hardened by the action of light (the unexposed parts) are then rubbed away with cotton, and the plate is chemically etched, gummed over, and dried. The plate is then ready to be printed from in a lithographic press. If a large map is to be reproduced it is photographed in parts, and contact prints are made on zinc plates. From these plates transfers are pulled and the parts are assembled and laid down in proper position on a stone or an aluminum plate, which is then prepared for printing.

A drawing that is to be reproduced by photolithography should be made on pure-white paper in lines, dots, or black masses with black waterproof ink. It should be one and one-half to two or three times the size of the finished print.

Photolithography is particularly adapted to the reproduction of maps, plans, and other large drawings. Within certain limitations, lines may be changed and details may be added after proofs have been submitted. The process is ordinarily used for reproducing illustrations in one color (black), but it is used also for printing in more than one color, generally over a black outline base, each color being printed from a separate stone, as in chromolithography.

OFFSET PRINTING.

In the offset process the design is "offset" from a lithographic plate or stone to a rubber blanket on a cylinder, from which it is printed. By thus obtaining an impression from an elastic surface the finest details can be printed on rough, uncoated paper, which can not be used in other processes, which can be folded without danger of breaking, and which is more durable than coated paper. Plates II, III, IV, VII, and VIII in this pamphlet were printed by this process.

CHROMOLITHOGRAPHY.

The chromolithographic process, by which illustrations are printed in color from stone, is used in Survey publications principally for reproducing geologic maps, but it is sometimes used for reproducing colored drawings of specimens.

There are several kinds of color printing from stones. One produces a picture by superimposing colors that combine and overlap without definite outlines and thus reproduce the softly blended colors of the original. Another reproduces the original by printing colors within definite outlines on a "base" which has been previously printed in black. The first kind is used by the Survey for reproducing colored drawings of specimens. The second is followed in reproducing geologic maps.

As each color must be printed from a separate stone and properly fitted with respect to the others a tracing from the original is made of the precise outlines of each color; or, if the design is to be reduced, a tracing is made over a properly reduced photographic print. This tracing can be made on specially prepared tracing paper or on a sheet of transparent gelatin or celluloid, which is laid over the copy and on which all the outlines and overlaps of the various colors are scratched with a steel point. The scratches thus made on the celluloid are filled with red chalk or like substance, and rubbed in with cotton, and by reversing the sheet and rubbing it the chalk lines are deposited on as many stones as are needed to produce the colors of the original design, each stone bearing all the outlines of the design. Sometimes all the outlines are engraved on what is called a key stone and an impression from it is laid down on each of the color stones. The parts on each stone that are to have one color are then inked in or engraved, and at the same time guide marks are indicated, so that in the composite print from the stones each color will fit its proper place. This fitting is called "register" and is an important part of printing, for each stone must be adjusted to a nicety while on the press in order to make each impression fit the others exactly. The process was originally manipulated entirely by hand, but photography has now replaced much of the handwork and has given rise to several methods by which the same kinds of subjects are reproduced in radically different ways. Tints are sometimes produced by the half-tone and other screens and by machine ruling, and printer's type is used almost exclusively for titles and other matter that was formerly engraved or drawn on the stone.

In reproducing a geologic map the base may be engraved on stone or on copper or it may be photo-lithographed. By either process the map may be transferred to the printing stone. The color stones for geologic maps are prepared by hand, but the geologic patterns, which are printed in colors, are engraved separately on plates, from which impressions are pulled when needed and transferred to their proper places on the printing stones in the shapes required according to the "key" design. The lighter, more transparent colors are generally printed first, and often twelve or more colors and many distinctive patterns are used to produce a geologic map. When proofs of such a map are pulled each stone must be taken up and carefully adjusted on the press, so that the work of proving maps that are printed from a considerable number of color stones is laborious and expensive. It is therefore customary to approve first combined proofs conditionally—that is, subject to the corrections and changes indicated on the proofs—and to hold the lithographer responsible for any failure to make the corrections.

This process is the most expensive one used for reproducing illustrations. Changes may be indicated on proofs, but changes can not be made on a stone twice in the same place without danger of affecting the printing or making it necessary to retransfer the parts affected. All changes are expensive because a slight modification at one point may involve corresponding changes on a number of stones, each of which must be taken up, corrected, and proved to insure the exact coincidence of the parts affected. It is often less expensive to retransfer the entire job than to make extensive changes on the original stones.

ENGRAVING ON STONE AND ON COPPER.

Engraving on stone is distinctly lithographic, but engraving on copper is sometimes included among lithographic processes because the work produced by it is usually printed from stone and thus becomes lithographic. In other respects engraving on copper is not a lithographic process. Roughly prepared maps and any rough line copy that is accurate in statement and clear as to intent are appropriate for both methods of engraving, but drawings that are expertly prepared are more suitable for reproduction by photolithography. In engraving on stone the lines of a design are scratched on the blackened surface of a stone with a steel-pointed tool; in engraving on copper the lines are cut with a graver on a sheet or plate of copper, the matter to be engraved being first shown on the plate by what is called the photo-tracing process, which was devised in the Geological Survey. There is, however, no great or essential difference in the printed results of the two processes, but most lithographers employ only stone engravers.

A stone on which a design is to be engraved is ground and polished according to the kind of work to be engraved, is coated with a thin solution of gum arable and allowed to dry, and is then washed until the superficial gum is removed while the surface pores remain filled. As the lines made by the engraver must be visible the stone is blackened with a pigment composed of lampblack and gum or is covered evenly with red chalk or Venetian red. It is then ready to receive the design to be engraved.

If the design is a map which is to show culture, streams, and surface contours, and each of these sets of features is to be printed in a separate color, impressions of the work to be engraved must be placed on three stones. One method of doing this is to make a scratch tracing of the original drawing on a sheet of transparent gelatin or celluloid in the manner employed in chromolithography, except that a dry pigment, generally chrome-yellow, is used to fill the scratch lines instead of red chalk or Venetian red. From this tracing a "faint" or imprint of all the details of the three separate features of the map is made on each of the three stones, and the engraver then cuts on each stone only the lines and other features, including ample register marks, that are to be printed in one color, the imprint made from the tracing making it possible to engrave each set of features in its exact position relative to the other two. By another method the matter to be engraved is photographed directly on the stone.

The engraving is done with a steel needle inserted in a small wooden cylinder, an instrument resembling an ordinary lead pencil. The size and shape of the needles used are varied according to the requirements of the matter to be engraved. With this instrument the lines and lettering are lightly scratched into the stone through the dark coating and show as light lines. The points of some of the needles are fine; those of others are V-shaped; and some have spoon-shaped points, for use in thickening lines and shading letters. All features are engraved in reverse.

After the engraving is completed the stones are prepared for printing by wiping off all the superficial color and filling the engraved lines with a greasy ink—generally a thin printing ink—which is rubbed into the lines with a soft rag. Impressions are then pulled on transfer paper and transferred to three printing stones for use in printing the three colors, the register marks enabling the pressman to fit each color exactly in its proper place.

In all lithographic processes the titles and other marginal lettering can be and usually are transferred from type impressions to the printing stones. It is therefore unnecessary to letter such matter carefully on an original drawing that is made for lithographic reproduction, for appropriate faces of type will give better printed results than hand lettering.

Corrections can not be made on a stone or copper engraving as readily as on a drawing. If a stone engraver makes an error or if a change is required after his engraving is finished, the parts to be corrected must be scraped off and a new ground laid before the correction can be made. Sometimes he will engrave the parts corrected on another part of the original stone and transfer it to the printing stone. Corrections are made on copper plates by "hammering up" the plate from beneath, polishing off a new surface, and reengraving the part to be corrected.

APPENDIX.

The matter given in this appendix is much used in making geologic maps and other illustrations. The Greek alphabet and the groups of signs presented are given chiefly to show the correct formation of each letter and sign.

MISCELLANEOUS TABLES.

Length of 1° of longitude measured along given parallels from the Equator to the poles. [From U. S. Coast and Geodetic Survey Report for 1884, Appendix 6.]

Parallel of latitude. Statute miles. 0 69.172 1 69.162 2 69.130 3 69.078 4 69.005 5 68.911 6 68.795 7 68.660 8 68.504 9 68.326 10 68.129 11 67.910 12 67.670 13 67.410 14 67.131 15 66.830 16 66.510 17 66.169 18 65.808 19 65.427 20 65.026 21 64.606 22 64.166 23 63.706 24 63.228 25 62.729 26 62.212 27 61.676 28 61.122 29 60.548 30 59.956 Parallel of latitude. Statute miles. 31 59.365 32 58.716 33 58.071 34 67.407 35 66.725 36 66.027 37 65.311 38 64.679 39 63.829 40 53.063 41 62.281 42 51.483 43 60.669 44 49.840 45 48.995 46 48.136 47 47.261 48 46.372 49 45.469 50 44.652 51 43.621 52 42.676 53 41.719 54 40.749 55 39.766 56 38.771 57 37.764 58 36.745 59 35.716 60 34.674 Parallel of latitude. Statute miles. 61 33.623 62 32.560 63 31.488 64 30.406 65 29.315 66 28.215 67 27.106 68 26.988 69 24.862 70 23.729 71 22.589 72 21.441 73 20.287 74 19.127 75 17.960 76 16.788 77 15.611 78 14.428 79 13.242 80 12.051 81 10.857 82 9.659 83 8.458 84 7.256 85 6.049 86 4.842 87 3.632 88 2.422 89 1.211 90 .000

Length of 1° of latitude measured along a meridian at given parallels. [Parallel given is in center of the degree whose length is stated.]

Parallel of latitude. Statute miles. Parallel of latitude. Statute miles.

0 68.704 50 69.115

10 68.725 60 69.230

20 68.786 70 69.324

30 68.879 80 69.386

40 68.993 90 69.407

Metric system and equivalents.

[The units of linear measure most commonly used are millimeters (mm.), centimeters (cm.), decimeters (dm.), meters (m.), and kilometers (km.), 1 m. = 10 dm.; 1 dm. = 10 cm.; 1 cm. = 10 mm.; 1 km. = 1,000 meters = 0.62137 mile; 1 m. = 39.37 inches = 3.280833 feet.]

Meters. Inches. Meters. Feet. Kilometers. Miles.

1 39.37 1 3.280633 1 0.62137

2 78.74 2 6.561667 2 1.24274

3 118.11 3 9.842500 3 1.86411

4 157.48 4 13.123333 4 2.48548

5 196.85 5 16.404166 5 3.10685

6 236.22 6 19.685000 6 3.72822

7 275.59 7 22.965833 7 4.34959

8 314.96 8 26.246666 8 4.97096

9 354.33 9 29.527500 9 5.59233

Inches. Centimeters. Feet. Meters. Miles. Kilometers.

1 2.54 1 0.304801 1 1.60935

2 5.08 2 0.609601 2 3.21869

3 7.62 3 0.914402 3 4.82804

4 10.16 4 1.219202 4 6.43739

5 12.70 5 1.524003 5 8.04674

6 15.24 6 1.828804 6 9.65606

7 17.78 7 2.133604 7 11.26543

8 20.32 8 2.438405 8 12.87478

9 22.86 9 2.743205 9 14.48412

The "vara," used in Texas, is equivalent to 33¹/₃ inches and is computed as representing 2.78 feet.

Geologic eras, periods, systems, epochs, and series.

Era. Period or system. Epoch or series.

Cenozoic. Quaternary. Recent. Pleistocene (replaces "Glacial").

Tertiary. Pliocene. Miocene. Oligocene. Eocene.

Mesozoic. Cretaceous. Upper (Gulf may be used provincially). Lower (Comanche and Shasta may be used provincially).

Jurassic. Upper. Middle. Lower.

Triassic. Upper. Middle. Lower.

Paleozoic. Carboniferous. Permian. Pennsylvanian (replaces "Upper Carboniferous"). Mississippian (replaces "Lower Carboniferous").

Devonian. Upper. Middle. Lower.

Silurian.

Ordovician. Upper (Cincinnatian may be used provincially). Middle (Mohawkian may be used provincially). Lower.

Cambrian. Saratogan (or Upper Cambrian). Acadian (or Middle Cambrian). Waucoban (or Lower Cambrian).

Proterozoic. Algonkian. Archean. pre-Cambrian.

Chemical elements and symbols.

Element. Symbol. Element. Symbol. Element. Symbol.

Aluminum Al Holmium Ho Rhodium Rh

Antimony Sb Hydrogen H Rubidium Rb

Argon Al Indium In Ruthenium Ru

Arsenic As Iodine I Samarium Sa

Barium Ba Iridium Ir Scandium Sc

Bismuth Bi Iron Fe Selenium Se

Boron B Krypton Kr Silicon Si

Bromine Br Lanthanum La Silver Ag

Cadmium Cd Lead Pb Sodium Na

Cesium Cs Lithium Li Strontium Sr

Calcium Ca Lutecium Lu Sulphur S

Carbon C Magnesium Mg Tantalum Ta

Cerium Ce Manganese Mn Tellurium Te

Chlorine Cl Mercury Hg Terbium Tb

Chromium Cr Molybdenum Mo Thallium Tl

Cobalt Co Neodymium Nd Thorium Th

Columbium C Neon Ne Thulium Tm

Copper Cu Nickel Ni Tin Sn

Dysprosium Dy Niton Nt Titanium Ti

Erbium Er Nitrogen N Tungsten W

Europium Eu Osmium Os Uranium U

Fluorine F Oxygen O Vanadium V

Gadolinium Gd Palladium Pd Xenon Xe

Gallium Ga Phosphorus P Ytterbium

Germanium Ge Platinum Pt (Neoytterbium) Yb

Glucinum Gl Potassium K Yttrium Y

Gold Au Praseodymium Pr Zinc Zn

Helium He Radium Ra Zirconium Zr

Greek alphabet.

Caps. Lower-case. Greek name. English sound. Caps. Lower-case. Greek name. English sound.

Α α Alpha. A. Ν ν Nu. N.

Β β Beta. B. Ξ ξ Xi. X.

Γ γ Gamma. G. Ο ο Omicron. O short.

Δ δ Delta. D. Π π Pi. P.

Ε ε Epsilon. E short. Ρ ρ Rho. R.

Ζ ζ Zeta. Z. Σ σ Sigma. S.

Η η Eta. E long. Τ τ Tau. T.

Θ θ Theta. Th. Υ υ Upsilon. U.

Ι ι Iota. I. Φ φ Phi. F.

Κ κ Kappa. K. Χ χ Chi. Ch.

Λ λ Lambda. L. Ψ ψ Psi. Ps.

Μ μ Mu. M. Ω ω Omega. O long.

Roman numerals.

I 1 IX 9 LXX 70 D 500

II 2 X 10 LXXX 80 DC 600

III 3 XIX 19 XC 90 DCC 700

IV 4 XX 20 C 100 DCCC 800

V 5 XXX 30 CL 150 CM 900

VI 6 XL 40 CC 200 M 1000

VII 7 L 50 CCC 300 MD 1500

VIII 8 LX 60 CD 400 MCM 1900

Mathematical signs.

+ plus. ~ difference

- minus. ∫ integration.

× multiplied by. ≎ equivalence.

÷ divided by. : ratio.

= equality. ∺ geometrical proportion.

± plus or minus. –: difference, excess.

□ square. ∴ therefore.

▭ rectangle. ∵ because.

∆ triangle. ∞ infinity.

◯ circle. ∝ varies as.

∠ angle. √ radical.

∟ right angle. ° degree.

⫍ or > greater than. ' minute.

⫎ or < less than. " second.

⊥ perpendicular.

NAMES OF ROCKS.

The following list was prepared in the geologic branch for the use of geologic draftsmen to enable them to select appropriate symbols for rocks that may be referred to in preliminary drawings by name only. For sedimentary rocks dots and circles, parallel lines, and broken or dotted lines are used; for metamorphic rocks short dashes arranged without definite patterns; and for igneous rocks patterns composed of short dashes, triangles, rhombs, crosses, and cross lines. All these patterns are shown in Plate III.

Sedimentary material.

[Including residual, detrital, eolian, glacial, organic, and chemically precipitated material.]

Agglomerate. Alabaster. Alluvium. Alum shale. Anhydrite. Apron (alluvial). Argillite. Arkose. Asphalt. Bench gravel. Bentonite. Boulder clay. Brea. Breccia. Brownstone. Burrstone. Calcarenite. Calc sinter. Caliche. Catlinite. Chalk. Chert. Clay. Coal. Conglomerate. Coprolite. Coquina. Detritus. Diatomaceous earth. Diluvium. Dolomite. Drift. Fan (alluvial). Fanglomerate. Flagstone. Flint. Freestone. Fuller's earth. Geyserite. Gravel. Graywacke. Greensand. Grit. Gumbo. Gypsum. Hardpan. Hematite. Infusorial earth. Ironstone (also igneous). Itacolumite. Kame. Kaolin. Laterite. Lignite. Limestone. Limonite. Loess. Marble (also metamorphic). Marl. Metaxite. Morainal deposit. Mudstone. Novaculite. Peat. Pelite. Phosphate rock. Phosphorite. Phthanite. Psammites. Psephites. Puddingstone. Pyroclastic material. Quartzite (also metamorphic). Reddle. Rock salt. Rock stream. Rubble. Salt. Sand. Sandstone. Selenite. Shale. Silt. Slate (also metamorphic). Soil. Stalactite. Stalagmite. Talc. Talus. Till. Travertine. Tripoli. Tufa (=chemically deposited lime). Tuff (=igneous fragments). Wacke. Wash.

Metamorphic material.

Adinole. Amphibolite. Andalusite schist (?). Apo (rhyolite), etc. Argillite. Augen gneiss (also igneous). Biotite schist. Calc schist. Cataclastic. Chlorite schist Clay slate. Damourite schist. Desmosite. Dynamometamorphic rock. Eclogite. Epidosite. Erlan. Erlanfels. Eulysite. Fibrolite schist Garnet rock. Garnet schist. Gneiss. Granite gneiss. Graywacke (?). Green schists. Greenstone (also igneous). Greisen. Halleflinta. Hornblende schist Hornfels. Hornstone. Itabirite. Kinzigite. Knotenschiefer. Knotty schists. Luxulianite (igneous?). Marble. Meta (diabase), etc. Mica schist. Mylonite. Ophicalcite. Ottrelite schist. Phyllite. Porcelanite. Protogene. Pyroschists. Quartz. Quartzite. Quartz schist. Schist. Sericite schist, etc. Serpentine. Slate. Soapstone. Sodalite. Spilosite. Steatite. Talc schist. Topazfels. Topaz rock. Zobtenite.

Igneous material.

Absarokite. Abyssal. Adamellite. Adendiorite. Ailsyte. Åkerite. Alaskite. Albitlte. Allivalite. Allochetite. Alnölte. Alsbachite. Ambonite. Amherstite. Analcitite. Andesite. Anorthosite. Aphanitite. Aplite. Arkite. Atatschite. Augen gneiss (also metamorphic). Augitite. Avezacite. Banakite. Banatite. Bandaite. Basalt. Basanite. Beerbachite. Bekinkinite. Bombs. Borolanite. Bostonite. Camptonite. Carmeloite. Cascadite. Chibinite. Ciminite. Comendite. Complementary rocks. Coppaelite. Cortlandite. Cromaltite. Cumberlandite. Cuselite. Dacite. Dellenite. Diabase. Diallagite. Dike rock. Diorite. Ditroite. Dolerite. Dunite. Durbachite. Effusive rock. Ekerite. Elvan. Enstatite. Eruptive rock. Essexite. Estrellite. Eulysite. Extrusive rock. Farrisite. Felsite. Felsophyre. Fergusite. Fortunite. Fourchite. Foyaite. Gabbro. Gauteite. Garewaite. Glumarrite. Gladkaite. Granite. Granitite. Granitoid. Granodiorite. Granophyre. Greenstone (also metamorphic). Greisen (?). Grorudite. Harrisite. Harzburgite. Haüynophyre. Hawaiite. Hedrumite. Heumite. Holyokeite. Hornblendite. Hypabyssal rock. Hyperite. Hypersthenite. Ijolite. Intrusive rock. Irruptive (=Intrusive) rock. Isenite. Jacupirangite. Jumillite. Kaiwekite. Kedabekite. Kentallenite. Kenyite.

Igneous material.—Continued.

Keratophyre. Kersantite. Kimberlite. Kobalaite. Krablite. Krageröite. Kulaite. Kyschytymite. Lamprophyre. Latite. Laugenite. Laurdalite. Laurvikite. Lava. Lestiwarite. Leucite basalt. Leucite tephrite. Leucitite. Leucocratic. Lherzolite. Limbergite. Lindoite. Liparite. Litchfieldite. Lithoidite. Luciitss. Lujaurite. Madrupite. Maenaite. Magma basalt. Malchite. Malignite. Mangerite. Mariupolite. Melaphyre. Melilite basalt. Mesanite. Mica peridotite. Minette. Missourite. Monchiquite. Mondholdeite. Monmouthite. Monzonite. Mugearite. Naujaite. Nelsonite. Nephelinite. Nevadite. Nordmarkite. Norite. Obsidian. Odinite. Orbite. Orendite. Ornöite. Orthophyre. Ortlerite. Ouachitite. Paisanite. Pantellerite. Pegmatite. Peridotite. Perknite. Perlite. Phanerite. Phonolite. Pierite. Pitchstone. Plagiaplite. Plagioclastic. Plumasite. Plutonic rock. Pollenite. Porphyry. Pulaskite. Pumice. Pyroxenite. Rhombenporphyry. Rhyolite. Rizzonite. Rockalite. Santorinite. Sanukite. Saxonite. Scyelite. Shastaite. Shonkinite. Shoshonite. Soda granite. Sölvsbergite. Sommaite. Spessartite. Sussexite. Syenite. Taimyrite. Tawite. Tephrite. Teschenite. Theralite. Tilaite. Tinguaite. Tjosite. Tonalite. Tonsbergite. Tordrillite. Toscanite (?). Trachy-andesite. Trachyte. Trap. Troctolite. Umptekite. Unakite. Ungaite. Urtite. Valbellite. Venanzite. Verite. Vitrophyre. Vogesite. Volcanic rock. Volhynite. Vulsinite. Websterite. Wehrlite. Windsorite. Wyomingite. Yamaskite.

INDEX.

[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [L] [M] [N] [O] [P] [R] [S] [T] [V] [W] [Z]

A. Abbreviations, forms of. 55-67 Adhesive materials, choice. 37 Alaska, maps of, reuse of. 17 Albertype. See Photogelatin processes. Apparatus, photographs of, preferred to sketches. 29 Approval of finished drawings, features to be covered by. 38 of illustrations, regulations governing. 80 Areas, patterns used to distinguish. 23 patterns used to distinguish, plate showing. 62 Army, Corps of Engineers of the, maps published by. 15 Artotype. See Photogelatin processes. Atlases, published, use of. 15 B. Base maps. See Maps, base. Bleaching photographic prints, method and solutions for. 69 Border for maps, width and use of. 57-58 Bristol board, kind Mid sizes used. 24, 66 Brash and pencil drawings, materials and methods used in making. 66-67, 69 Brushes, kinds and sizes used. 66-67,71 C. Celluloid transferring, process of. 47 requisitions for. 47 Cerotype process, description and advantages of. 80-81 Changes in engravings, possible kinds of. 38-39, 90 Changes in original material, draftsman to consult author on. 65 Chemical elements, names and symbols of. 93 Chromolithography, description of. 87-80 Civil divisions, lettering of. 53, 54 Coal beds, indication of thickness of. 31 Coast and Geodetic Survey charts, use of. 15 Collotype. See Photogelatin processes. Coloring materials, use of. 26 Colors, standard, for geologic maps. 62-63 use of, for ground-water features. 21-23 on original geologic maps. 27-28 Commas, form of. 54 use of, in numbers. 54 Contours, drawing of. 48-50 Cooperation, mention of. 13 Copper, engraving on. 89, 90 etching in relief on, process and advantages of. 75 Copying methods of. 46-48 Corrections. See Changes. Cost of photo-engravings. 75, 78, 80, 81 County maps, use of. 15 Crayons, wax, use of. 26, 50, 51 Credit for data of maps, indication of. 13 Crystals, drawings of, making and lettering of. 70 Cultural features, lettering of. 53-54 list of. 52-53 Curves, date showing. 64 Cuts. See Engravings. D. Details of a geologic map, plate showing. 58 Diagrams, drawing and lettering of. 64 features of, plate showing. 64 original, general requirements for. 28-20 Director of the Survey, order by. 9 Divisions of plates and figures, serial letters and numbers for. 12 Drafting table, shadowless, description of. 47-48 shadowless, use of. 29, 48, 50 Draftsmen, detail of, to aid author. 9 detail of, to prepare base maps. 13-14 experience and reading required by. 41-42 general treatment of material by. 42-43 Drainage features, depiction of. 51-52 Drawing instruments, list of. 42 Drawing materials, kinds used. 23-26, 66-67, 69, 71 Drawings, authors', draftsmen may aid in making. 9 authors', editorial revision of. 38 finished, general requirements for. 41-42 requests for photographs of. 34 Duplicates of engravings, charges for. 38 E. Effectiveness of illustrations, elements that produce. 7, 30 Electrotypes of engravings, charges for. 38 Elements, chemical, names and symbols of. 93 Engraving on stone, process of. 89-90 See also Lithography. Engravings, changes in. 38-39 original, time of keeping. 37 Erasers, injury to paper by. 67 kinds used. 25, 67-68 Erasures, smoothing paper after. 68 Explanations on maps, arrangement and lettering of. 19, 58-50 F. Figures, differences from plates. 10-11 divisions of, serial letters for. 12 methods of inserting, plate showing. 12 Formations, geologic, use of letter symbols for. 20-21 Fossils. See Specimens. Four-color process, advantage of. 80 G. Gas wells, symbols for. 21 Generalization, true, meaning of. 17 Geographic tables and formulas (Bull. 650), use of. 44, 45 Geologic periods of time, names of. 92 Gouache, use of. 67, 69 Great Lakes surveys, maps published by. 15 Greek letters, forms, names, and English sounds of. 93 Ground-water features, symbols representing. 21-23 H. Hachuring, use of. 50 Half-tone engraving, preparation of copy for. 77-78 process and advantages of. 75-78 three-color process of. 78-80 Half tones, changes in. 39 prints of, showing effects produced by different screens. 56 requirements for printing. 11 Heliotype. See Photogelatin processes. Hill shading, use of. 60-51 Hydrographic features, lettering of. 54 representation of. 51-52 Hypsographic features, lettering of. 54 I. Illustrations, kinds of. 10-11 Inks, kinds used. 25, 67 methods of using. 25 Inserting plates and figures, methods of, plate showing. 12 Instruments, draftsmen's, list of. 42 J. Japanese transparent water colors, use of. 26 L. Land Office maps, scales and detail of. 14-15 Latitude, length of 1° of, at intervals of 10°. 91 Lending of photographs and drawings, rules governing. 34 Letter symbols, use of, on geologic maps. 20-21 Lettering, directions for. 53-55 for lithographing. 90 for names of streams. 52, 54 on diagrams. 64 on drawings of crystals. 70 on original maps. 19 on plans and cross sections of mines. 65-66 reduction sheet used in, plate showing. 54 use of type for. 54-55 Light, direction and gradation of. 66 Lithographs, printing and insertion of. 11 Lithography, original process of. 83-85 See also Engraving on stone. Longitude, length of 1° of, at latitudes 0° to 90°. 91 M. Map of the world, millionth-scale, use of, for base maps. 14 Maps, areal patterns for, drawing of. 61-62 bar scales for. 59-60 base, conventional symbols used on. 45-46 including new data, how obtained. 13-14 indication of sources on. 13 of the United States on small scales, use of. 15 published maps available for. 14-17 reuse of, to be approved. 13 black and whits, patterns used on, plate showing. 62 borders for. 57-68 cultural features on. 52-53 enlargement and reduction of. 18 explanations for. 19, 58-59 geologic, details of, plate showing. 58 printing of. 87-89 standard colors for. 62-63 hydrographic features on. 61-52 lettering on. 53-65 materials used for drawing. 23-28 orientation of. 18 original, margin required on. 19 original base, amount of detail on. 17 must be free from colors and symbols. 28 preparation of. 13-14, 17-18 original geologic, method of coloring. 27-28 projection for. 18-19, 43-45 reduction or enlargement of, marking for. 63-64 relief on. 48-51 standard scales for. 18 symbols used on. 20-23 drawing of. 61 plates showing. 20, 46 titles for. 58 topographic, scales of. 14-15 Mathematical signs, forms and names of. 94 Measures, linear, metric equivalents of. 92 Measuring scales for map projection, use of. 44 Meridians used on public-land maps, diagram showing. 16 Metric measures, English equivalents of. 92 Millionth-scale map, use of. 14 Mine plans, conventional lines for. 29 features of. 65-66 symbols used on, plate showing. 20 Minerals. See Rocks. Mississippi River Commission, maps published by 15 N. Names of rocks. 94-97 National forest maps and proclamations, use of. 15 O. Offset process, description of. 87 Oilwells, symbols for. 21 Opaquing, meaning of. 18, 47, 86 Orientation of maps, requirements for. 18 Original drawings, general treatment of, by draftsmen. 42-43 preparation of. 12-40 Outdoor sketches, redrawing of. 69-70 P. Panoramas, construction of. 71 Paper, kinds used for drawings. 23-24, 60, 61, 66, 69 Pastes, use of. 37 Patterns, areal, method of drawing. 61-62 areal, plate showing. 62 Pen drawings, materials and methods used in making. 67-68, 68-69 Pencils, colored, use of. 26 drawing, quality and grades of. 25, 66 Pens, kinds of, used for drawing. 25, 48, 67 Photoengraving, cost of. 75, 78, 80, 81 general features of. 72-73 Photoengravings, printing and insertion of. 11 Photogelatin processes, description of. 82-83 Photographs, adaptation of. 83 bleaching of. 69 care needed in taking and handling. 32, 33, 39-40 copyrighted, consent for use of. 33-34 duplicate prints of, requests for. 34 mounting and numbering of. 33, 36-37 poor, mating of drawings over. 68-69 preparation of, for half-tone engraving. 77-78 record of source of. 34 selection of. 32-33 retouching of. 68, 70-71 suitability of. 9 unpublished, issue and use of. 34 Photolithographs, changes in. 39 Photolithography, description of. 86-87 Planographic process, description of. 87 Plans of mines, drawing and lettering of. 29, 65-66 symbols used on, plate showing. 20 Plates, differences from figures. 10-11 divisions of, serial letters and numbers for. 12 grouping small illustrations on. 36-37 methods of inserting, plate showing. 12 Political divisions, lettering of. 53, 54 Post-route maps, scales and detail of. 15 Projection for maps, preparation and checking of. 18-19, 43-45 Proofs, changes in. 76 correction of. 38-39 duplicate, supplying of. 30 submittal of. 38 Public-land maps, meridians, parallels, and township lines used on, diagram showing. 16 Public works, lettering of. 53 Punctuation marks, forms of. 54 Purpose of illustrations in Survey reports. 8, 40 R. Railroad surveys, data for maps obtainable from. 15 Railroads, names of, on maps. 57 Reduction of maps, marking drawings for. 63-64 means of. 18 Reduction sheet for lettering, plate showing. 54 use of. 55 Relief, methods of expressing. 48-51 Reproduction of illustrations, processes for. 72-90 relation of, to the drawing supplied. 7, 40 Reticulation, sketching by. 47 Retouching of photographs, materials and method used in. 68, 70-71 Reuse of illustrations, procedure for. 37-38 Rocks, igneous, names of. 95-97 metamorphic, names of. 95 sedimentary, names of. 94-95 symbols used to distinguish. 32 See also Specimens. Roman numerals, numbers expressed by. 93 Rubber, liquid, use of. 37 S. Scales, bar, forms of. 50-60 measuring for projection of maps. 44 standard, of maps. 18 Scope of this manual. 7 Screens, half-tone prints showing effects produced by. 56 Selection of illustrations, considerations governing. 8-9 Sections, columnar, original drawings for. 31 columnar, symbols used in, plate showing. 32 structure, combination of, with views of topography. 30-31 drawing of. 64-65 original drawings for. 29-31 symbols used in, plate showing. 32 vertical exaggeration of. 30 Shading, kinds used. 67 Signs, mathematical, forms and names of. 94 Sises of illustrations. 11-12, 40 Specimens, borrowed and fragile, care of. 35 drawings of, methods of making. 60-68 paleontologic, transmittal of. 35 photographs of, how printed. 68 how used. 34-85 Springs, symbols for. 22, 23 State maps, use of. 15 Stipple, production of. 50, 51 Stone, engraving on. 89-90 Streams, drawing of. 51-52 lettering names of. 52 Submittal of illustrations. 10 Symbols, drawing of. 20, 61 for ground-water features, uniformity needed in. 21-23 for maps and mine plans, plates showing. 20, 46 uniform use of. 20, 45-46 for oil and gas wells, features of. 21 for structure and columnar sections, plate showing. 32 lithologic, use of. 32 T. Three-color half-tones, process of making. 78-80 Titles of illustrations, arrangement and place of. 58 printing of. 19-20 wording and lettering of. 19 Tooling on half-tones, effects obtained by. 77, 78 Topographic atlas sheets, scales of. 14 Tracing, method of. 46-47 use of colors in. 46-47 Tracing linen, use of. 24-25 Transferring, celluloid, process of. 47 celluloid, requisitions for. 47 Type, lettering with. 54-55 styles and sizes of. 55 V. Value of illustrations in Survey reports. 8 Vara, length of. 92 Vignetting, effect obtained by. 78 W. Wall map of the United States, use of, for basemaps. 14 Water colors, use of. 26, 67, 71 Waterlining, use of. 52 Wax engraving, process and advantages of. 80-81 Wells, symbols for. 22, 23 Wood engraving, process of. 81-82 Z. Zinc etchings, changes in. 38-39 drawings for. 74 insertion of. 11 making and advantages of. 73-75

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Transcriber's Note

Paragraphs split by illustrations were rejoined.

In the table of Mathematical symbols, the symbol for "varies as" was set to the unicode symbol for "proportional to" (&#8733; = ∝).