N. for north, NE. for northeast, NNE. for north-northeast, etc.

Capitalize directions affixed to street names, as NW., SE.

(1800 F St. NW.).

Sec. and secs. for section and sections before a number.

Capitalize only at the beginning of a line or sentence.

a. m. and p. m. for antemeridian and postmeridian, as 4.30 p. m.

Lower-case unless in line of caps.

& in names of corporations or companies. On Survey miscellaneous

maps "and" is spelled out in railroad names.

B. t. u. for British thermal units.

bbl., bbls. for barrel, barrels.

bu. for bushel or bushels.

c. c. for cubic centimeter.

cm. for centimeter.

cwt. for hundredweight.

dwt. or pwt. for pennyweight

oz. for ounce or ounces.

etc. (not &c.) for et cetera.

ft. for foot or feet.

H. m. s. for hours, minutes, and seconds. (Use capital H.)

in. for inch or inches.

kw. for kilowatt or kilowatts.

£ s. d. for pounds, shillings, and pence.

per cent (omitting period) for per centum. Spell out percentage.

ser. for series.

St. for Saint or street

U. S. Army for United States Army, as distinguished from United

States of America (U. S. A.).

yd., yds. for yard, yards.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VI

175-LINE SCREEN 150-LINE SCREEN

133-LINE SCREEN 120-LINE SCREEN

100-LINE SCREEN 65-LINE SCREEN

HALF-TONE CUTS SHOWING EFFECT OF SEVERAL STANDARD SCREENS IN THE

REPRODUCTION OF THE SAME DETAIL.]

The names of certain months may in some places be abbreviated; those

of others should invariably be spelled out. The following are the

correct forms:

Jan. Apr. July Oct.

Feb. May Aug. Nov.

Mar. June Sept Dec.

The abbreviations for number and numbers before figures are No. and

Nos. The o should never be raised, as in N^o. The abbreviation for Mac

is Mc, not M^c.

All periods should be omitted from abbreviations used in the body of a

map unless their omission would cause misunderstanding. They are

generally unnecessary, and if used on some maps they are likely to be

mistaken for symbols representing certain features, such as houses or

flowing wells, if either is shown. Periods used on drawings that are

to be reproduced "direct" or photomechanically should always be

slightly exaggerated.

NAMES OF RAILROADS.

The names of railroads may be written in full or abbreviated, in

accordance with the kind of map and the space available. On a sketch

map in black and white the initial letters are generally sufficient.

On a more detailed map, if there is room enough, the names may be

spelled out. As already stated, neither the words "railroad" and

"railway" nor the abbreviations R. R. and Ry. should be used on a map.

MAKE-UP OF MAPS.

FORMS FOR CERTAIN FEATURES.

The proper forms for certain features of maps, such as the borders,

titles, explanations, bar scales, captions, arrows indicating true

north and magnetic declination, source, and authorship, are shown in

Plate VII. Note particularly the style and position of the marginal

matter.

BORDER.

A finished map border is used or omitted according to the kind of map

prepared. Diagrammatic maps and maps on which no parallels and

meridians appear do not need finished borders. On a map that shows

complete areal geologic or other coloring, such as a map in a Survey

geologic folio, the border lines tend to destroy the simple effect of

the whole map. On a map that is not completely colored and on all very

large maps borders are really necessary. If borders are used, however,

the space between the neat line and the outer line of the border

should be only sufficient to provide proper space for the numbers

showing latitude and longitude or township and range. A simple rule[8]

for determining the width of this space is as follows: Divide the sum

of the dimensions of the map by 2 and find the square root of the

quotient, which will represent the width of the border in sixteenths

of an inch. Example: Map is 20 by 30 inches; (20 + 30)/2 = 25; square

root of 25 = 5; width of border = 5/16 inch.

[Footnote 8: Worked out by Martin Solem, of the U. S. Geological

Survey.]

The numbers showing latitude and longitude should be in shaded arabic

numerals and those showing township and range in gothic. The symbols

for degree, minute, and second should not be crowded. On a map that

has no added border lines the numbers should be in hair-line gothic.

TITLE.

The title of a map should be in roman letters and if placed at the

lower margin should generally be arranged in two lines, unless it is

short. If it forms two or more lines the lines should be well

balanced. The first line should describe the position of the area; the

second line should state the purpose of the map, as

MAP OF BUTTE AND VICINITY, MONTANA

SHOWING LOCATION OF MINES AND PROSPECTS.

A title placed inside the border of a map should be arranged in a

series of lines, generally beginning with "Map of" or "Geologic map

of." and the line showing the dominant part of the title should be

emphasized by larger lettering, thus:

=MAP OF=

THE VICINITY OF BUTTE

MONTANA

SHOWING LOCATION OF MINES AND PROSPECTS.

The name of the author or compiler of a map or of the person supplying

the geologic or other data shown on it may be placed either beneath

the title or in the lower right corner, just below the border line,

and the names of the topographers or the source of the base should be

stated in the lower left corner, just below the border line. If the

title is placed inside the border all notes giving credit for any part

or features of the map may be placed beneath the title or scale. (See

PI. VII.)

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VII

DETAILS OF THE MAKE-UP OF A GEOLOGIC MAP]

EXPLANATION.

The symbols, patterns, or colors used on a map should be given in a

series of rectangles or "boxes," accompanied by explanatory terms in

the form shown in Plate VII, headed "Explanation." If the explanation

is small a convenient place for it on some maps may be found within

the neat lines. If no space is available there, or if it is so large

that there is not room to place it there without obscuring other

details, it may be placed either vertically along the right margin, as

shown in Plate VII, or horizontally under the title. A geologic

explanation should preferably be arranged vertically, as in Plate VII,

so as to show the relative age of the formations by the positions of

the boxes. This explanation should be carefully worked out in pencil

by the draftsman and approved by the committee on geologic names

before it is drawn in ink, in order to save time in making

corrections.

In lettering the explanation roman letters or type should be used for

the titles under the boxes and italic of smaller size for the

subtitles or descriptive detail, which should be inclosed in

parentheses. The names of geologic periods and systems should be in

gothic capitals, the names of series or groups should be in italic

lower case, and the limit of each period, system, or group should be

indicated by braces. The general style and arrangement shown in the

Survey's geologic folios should be followed, and this and the

arrangement of other matter is shown in Plate VII. Care should be

taken not to crowd the explanation, and if corrections are necessary

they should be so made that each line of the matter in which they

appear will be properly spaced.

The explanation for a map that is to be engraved or to be reproduced

by lithography need only be sketched in to show general style and

arrangement. The engraver or the lithographer will supply such matter

in proper form according to specifications. For direct reproduction,

however, as by photolithography or zinc etching, the lettering must

either be carefully drawn with pen or printed from type on slips,

which are pasted on the drawing.

GRAPHIC SCALES FOR MAPS.

A bar scale for miles or feet should be given on every map, and if the

map is of international interest the metric scale should be given just

beneath the scale of miles or feet. The accepted designs for these

scales are shown in figure 7. The scale should be accompanied by any

necessary statement pertaining to the base map, such as "Contour

interval 20 feet," "Datum is mean sea level." The fractional scale

(1/250,000, for example) should be given on all except the more simple

kinds of maps, and the date of publication should also appear just

below the scale or scales. The single-line bar scale should be used

only on small or simple maps. The length of the bar scale must depend

on the size of the map and the space available. Those shown in figure

7 were made over blue prints from scales used by the Survey.

To make a bar scale for a map of unknown scale that shows only a

single meridian and parallel, or for a map on which no meridians or

parallels are shown, first ascertain the distance between two points

shown on the map by reference to other authentic maps. If, for

example, the distance between two such points is 16.315 miles draw a

horizontal line (_a_ in fig. 8) representing this distance on the map,

and at its end, at right angles to it, draw another line (_b_)

actually measuring 16.315 units of any convenient denomination. Draw a

straight line (c) diagonally between the ends of lines _a_ and _b_.

Then set off on line _b_ any convenient number of the units selected,

say 5 or 10, and project from the points set off lines exactly

parallel with line _c_ to line _a_. The distance and the number of the

units thus marked on line a will indicate the number of miles covered

by that distance on the map, as shown in figure 8.

[Illustration: Figure 7.--Designs for bar scales.]

[Illustration: Figure 8.--Method of making a bar scale for a map of

unknown scale.]

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VIII

PATTERNS USED TO SHOW DISTINCTIONS BETWEEN AREAS ON BLACK AND WHITE

MAPS

Contrasts may be increased by varying the direction and spacing of

Lines]

SYMBOLS.

Symbols should be drawn with as much care as letters, though to a

critic they may not appear so bad as poor lettering unless he finds

them glaringly large or so small that he can discover or identify them

only with difficulty. The size of a symbol must depend on its

importance on the map bearing it. On a map that shows numerous mines,

for instance, the crossed hammers or the symbols for shafts should be

not only visible but conspicuous. The draftsman who is to make such a

map must know beforehand how much his drawing will be reduced in

reproduction and must make the symbols in proportion to the reduction.

The symbols shown in Plate II (p. 20) should be used in all the

Survey's illustrations where they are appropriate.

AREAL PATTERNS FOR BLACK AND WHITE MAPS.

The conventional patterns used on a map to distinguish separate areas,

chiefly geologic, are shown in Plate VIII. The patterns shown

represent the proper combinations of lines, dots, and other forms and

should be spaced openly or closely according to the size of the area

covered, the contrast needed between areas, and the general clearness

and effect desired. If a map is to show both small and large areas

dense or closely spaced patterns should generally be used for the

smaller areas, even if they may be required for some fairly large

areas representing the same formation or condition. On the other hand,

open patterns should be used for large areas. Again, it may be

necessary to make certain areas more conspicuous than others, and this

effect can be best produced by drawing the lines closer together

rather than by making them heavier, unless the area covered is small

or unless a closely spaced similar pattern has been or will be used

elsewhere on the map. Heavy-line patterns or bars are not desirable.

The lines forming a pattern should generally be drawn at an angle of

45° to the sides of the map; they should be drawn vertically or

horizontally only in small areas or in areas not crossed by meridians

or parallels or by other lines running in the same direction. The

lines should preferably run across the long axis of an area, not

parallel to it, and the predominating trend or general direction of

the areas of one geologic formation on a map should decide the

direction of the lines for all areas of that formation on the same

map, even if the rule must be violated on some of the minor areas.

An effort should always be made to produce a pattern that is

subordinate in strength to the main lines of the base map on which it

is drawn. In black and white maps, as in colored maps, unlike patterns

should be placed next to each other. If they are so placed it may not

be necessary to rule the lines on two adjacent areas in opposite

directions to produce needed distinctions. A section liner or other

ruling device should be used in drawing line patterns in order to

produce uniformly even spacing. The application of six of these

conventional patterns to a base map is shown in figure 9.

[Illustration: Figure 9.--Map bearing six areal line patterns.]

STANDARD COLORS FOR GEOLOGIC MAPS.

The standard series of colors for systems of sedimentary rocks is

shown on the maps in the Survey's geologic folios but is subject to

modifications for use on maps in other Survey reports. Each system is

represented by a different color, and if there are two or more

formations in one system they are generally distinguished by using

different patterns composed of straight parallel lines in the same

color. The patterns for subaerial deposits (chiefly Quaternary) are

composed of dots or circles, or combinations of both, and may be

printed in any color, but the color most often used is yellow or

ochraceous orange. No specific colors are prescribed for igneous

rocks, but if only a few areas are shown red or pink is preferred. The

colors used for igneous rocks are generally more brilliant and purer

than those used for sedimentary rocks. For small areas they are used

"solid"; for large areas they are reduced in tone by the use of a

suitable cross-line pattern or "reticle." Metamorphic rocks are

represented by short dashes irregularly placed. These dashes may be in

black or in color over a ground tint or over an uncolored area, or

they may be in white on a ground tint or pattern. The standard colors

used for the sedimentary series covering the 12 systems recognized by

the Geological Survey are: Quaternary (Q), ochraceous orange; Tertiary

(T), _yellow ocher_ and _isabella color_; Cretaceous (K),

_olive-green_ or _rainette-green_; Jurassic (J), _blue-green_ or

_niagara-green_; Triassic (TR), _light peacock-blue_ or _bluish

gray-green_; Carboniferous (C), _blue_ or _columibia-blue_; Devonian

(D), _gray-purple_ or _heliotrope-gray_; Silurian (S), _purple_ or

_argyle-purple_; Ordovician (0), _red-purple_ or _rocellin-purple_;

Cambrian (-C), _brick-red_ or _etruscan red_; Algonkian (A), _terra

cotta_ or _onion-skin pink_; Archean (AR), _gray-brown_ or _drab_.[9]

[Footnote 9: Names printed in italic are from "Color standards and

nomenclature," by Robert Ridgway.]

REDUCTION OF ENLARGEMENT OF MAPS.

The following is the simplest and most accurate method of marking the

reduction or enlargement of a map to a selected scale: Measure the

distance between the extreme meridians along one of the parallels.

(See fig. 10.) Convert this distance into miles by multiplying the

number of degrees it covers (say 3) by the number of miles in a

degree. A degree on the forty-third parallel, for example, is 50.669

miles,[10] which multiplied by 3 equals 152.007 miles. Then draw a

line on the margin of the map, outside the border, the exact length of

the 3 degrees, and just below this line draw another line representing

the same number of miles (152.007) on the scale to which the map is to

be reduced or enlarged. Then mark to reduce or enlarge the upper line

to the lower line, as shown in figure 10. A long line will reduce

error and give greater accuracy than a short one, and therefore as

great a distance should be set off as possible. The number of miles

represented by both lines and the fractional scale to which it is to

be reduced should be stated on the drawing, for permanent record.

[Footnote 10: See U. S. Geol. Survey Bull. 650, p. 37. 1916.]

Maps that will bear reduction without affecting the clearness of the

details they show may be reduced to fit the book in which they are to

appear, regardless of definite scale. The reduction for such maps is

best marked in fractions, as "1/2 off," "1/3 off," "2/3 off." If the

size needed is not exactly represented by these fractions it should be

indicated in inches, as "Reduce this line to 7-1/2 inches," or "Reduce

to 4-3/8 inches in width."

[Illustration: Figure 10.--Diagram showing method of marking maps for

reduction or enlargement (for record).]

DIAGRAMS.

In preparing a diagram a draftsman should endeavor to make its parts

and relations perfectly clear to the reader. He should study the

drawing or material furnished by the author until he fully understands

it and should endeavor to reproduce it simply and legibly. Any

lettering that may be needed should generally be in plain upright or

slanting gothic type (see Pl. IX), or it may be in roman.

A diagram should generally be drawn on bristol board or on blue-lined

section paper and should be marked for reduction to the minimum size.

It should bear no title, as the title will be set up in type by the

printer.

SECTIONS.

The sections used in geologic reports are of two widely different

kinds. One shows only the broader relations of parts; the other shows

details of structure as well as relations. One is diagrammatic; the

other is more realistic and graphic. The draftsman should prepare all

sections strictly according to the copy supplied by the author but

should use proper symbols and make a more finished drawing. The

various kinds of sections, most of them geologic, are described on

pages 29-30, and the conventions used to express lithologic character

are shown in Plate III.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VIII

DIAGRAMS AND CURVES.]

Detailed drawings of this kind, though entirely conventional, can be

so prepared as to give a satisfactory expression of nature. The

draftsman should study well-prepared sections in Geological Survey

reports and should learn the details of folding and faulting from

textbooks. He should first ascertain whether or not the vertical scale

in the original section has been unduly exaggerated, and if so he

should confer with the author with a view to reducing the exaggeration

as much as possible. He should submit to the author all questions as

to doubtful points, as well as all suggestions for improvement in

expression, before he makes any changes, and he should make

corrections only on the author's approval. A seeming inaccuracy in an

author's drawing may be a faithful representation of natural

conditions. For example, a formation that seems to be omitted by

inadvertence in drawing may really "pinch out" at a point represented

in the section. (See a on fig. 11.)

[Illustration: Figure 11.--Structure section showing method of

determining the secession of folds.]

Penciled lines corresponding to those shown by dots in figure 11

should be carefully added in redrawing a roughly sketched section that

shows complex folding. An original indefinite sketch that shows

complicated structure affords opportunities for error in preparing the

new drawing, and omissions may be detected by following the formations

as they would be continued above and below the section, as shown by

the dotted lines in the figure.

PLANS AND CROSS SECTIONS OF MINES.

Plans of mines, like diagrams, should not be elaborate, and their

lettering should be plain and legible, yet it should not be so

conspicuous as to obscure other details. Gothic letters should

generally be used, but some plans require different styles of

lettering, especially for geographic or other names that should be

coordinate with those on maps or other illustrations in the book.

Unless there are good reasons, however, for varying the styles of

lettering, plain gothic capitals, or capitals and lower-case letters,

either upright or slanting, should be used. Abbreviations for the

numbers of levels should generally be given thus: 3d level, 6th level,

200-foot level, etc., or the shorter terms may be spelled out, as

third level, sixth level. The same general scheme of lettering should

be used on all plans and cross sections that are to appear in one

publication or in one series of similar papers.

The reduction of such drawings to the minimum scale consistent with

clearness is always advisable.

DRAWINGS OF SPECIMENS OF ROCKS AND FOSSILS.

METHODS USED.

Drawings of specimens or other objects were once made with brush and

pencil or with pen and ink, by means of measurements taken with

dividers or by viewing the specimen through a camera lucida. Each of

these methods is still used, but by using the camera lucida in

sketching: the outlines and details more accurate proportions and

relations can be produced, whether the object is to be enlarged or

reduced, than by any other means except photography.

BRUSH AND PENCIL DRAWINGS.

In all drawings or photographs of specimens, except photomicrographs

of thin sections, the light should appear to come from the upper left

quarter. A disregard of the well-established rule that the direction

of illumination should be uniform throughout a series of drawings

would cause confusion or uncertainty in the interpretation of the

relief shown in them.

Reynolds's three-ply and four-ply bristol board affords a satisfactory

surface for brush and pencil drawings. Its surface is smooth and hard

and, being free from coating of any kind, permits satisfactory

erasures without great injury; its color is pure whits; and it is

durable.

Boss's relief hand-stipple paper is also well adapted to many kinds of

brush drawings as well as to its primary use for producing stippled

effects. Very delicate gradations of color or light and shade can be

produced on its surface with brush and lampblack or with india ink,

and high lights can be made by scraping off the chalky surface.

The draftsman who is preparing brush and pencil drawings should have

first of all a knowledge of the principles of light and shade, of

reflected light, and (for drawing specimens) of shadow perspective. He

should also have delicacy of touch and ability to see and interpret

form and to reproduce the soft blending of light and shade shown in a

good photograph. He should be provided with pencils equal in quality

to the Koh-i-noor B, F, 4H, and 6H; the best quality of red sable

brushes of the sizes of Winsor & Newton's Nos. 3, 4, and 6; the best

quality of stick india ink; a cake or pan of lampblack; and a

porcelain saucer or slab.

In drawings of fossils and of some other specimens a combination of

pencil and brush work produces satisfactory results and tends to

increase speed. The gloss produced by penciling, however, is

objectionable and should be obviated by a preponderance of brush work.

Stick India ink is the best pigment to use in delicate wash drawings,

and lampblack is preferable for large work on which the softer tones

of the shading are not so important and for drawings that are to be

considerably reduced when engraved. Gouache (an opaque mixture of

Chinese white and lampblack) may also be used, but it is best suited

for large work.

In making corrections on brush drawings the parts to be corrected

should be carefully washed out with a small short-cropped brush and

water and still further cleaned by using a rubber eraser over an

erasing shield or an opening cut in a piece of celluloid. Erasures

should not be made on delicate work with a knife or a sand rubber, as

either will injure the surface and affect reproduction. In measuring a

specimen with dividers the draftsman should be careful not to injure

the specimen or to puncture the paper on which he is preparing the

drawing.

PEN DRAWINGS.

A draftsman who is preparing drawings of specimens with pen and ink

should have a good assortment of pens equal to Gillott's Nos. 291,

290, and 170, liquid waterproof ink equal to that manufactured by

Higgins, good pencils, hard and soft rubber erasures, plain dividers,

and Reynolds's bristol board. A glass eraser is also useful.

Good pen drawings of specimens are much more difficult to make than

brush drawings. They can be prepared only by a draftsman who has had

some artistic training and experience in pen work. Few draftsmen can

prepare pen drawings that faithfully represent both the detail and the

texture of specimens; the shading on many such drawings confuses and

destroys both detail and texture.

The pencil sketch over which a pen drawing of a specimen should be

made must be prepared in much the same manner as the sketch for a

brush drawing, though the outlines need not be so delicate. This

sketch is generally made on bristol board. The pen work should begin

with the outlines and should then be carried to the details, and

finally to the shading, whether in lines or stipple. The texture of a

specimen is the best key to the proper shading. If the specimen is

decidedly granular, stippling is appropriate; if it is smooth or

polished, finely drawn parallel lines, varied in spacing and

character according to depth of shade and texture, are preferable.

Erasures can be made with a hard-rubber eraser, other parts being

protected by a shield, or with a very sharp knife or a glass eraser,

and the parts erased can be resurfaced with an agate burnisher.

RETOUCHING PHOTOGRAPHS OF SPECIMENS.

Photographs of specimens, particularly fossils that have been coated

to destroy local color, should be printed on velox paper, in a tone

somewhat lighter than that of ordinary photographs. The details and

relief should, however, be strong enough to enable the draftsman to

see them clearly, so that by retouching them and strengthening the

shadows and high lights he can make them sufficiently strong for

reproduction. This he can do by a combination of pencil and brush

work, the pencil being used sparingly because the gloss produced by

the graphite is likely to affect reproduction. A No. 3 Winsor &

Newton's red sable brush and lampblack are preferable for the greater

part of this work, and a 4H and a 6H pencil for the fine details and

as a possible aid in producing the finer gradations of shading. The

details should be retouched or strengthened under a reading glass to

insure accuracy; the broader effects can be best produced without the

aid of a magnifier.

Erasures on photographs of specimens should be made very carefully

with a hard rubber that is free from sand, and the parts not to be

disturbed should be protected with a shield. High lights may be added

by carefully scraping or rubbing the surface of the paper.

LANDSCAPE DRAWINGS FROM POOR PHOTOGRAPHS.

A poor photograph or one that has become injured and can not be

retouched for direct reproduction can be utilized by making from it,

as described below, a pen drawing or a brush or crayon drawing, which

will be almost photographically correct.

PEN DRAWINGS MADE OVER PHOTOGRAPHS.

A pen and ink drawing may be made over a blue print or a bromide print

(preferably a blue print) and the photographic image then bleached

out. The blue print should be larger than publication size and should

not be so dark that the draftsman can not see his lines. If the

negative is available a bromide enlargement can be obtained; otherwise

the picture should be rephotographed in larger size, preferably twice

publication size. The enlargement will give the draftsman greater

freedom in drawing details and will make his work appear finer and

better in the reduced illustration. If the photographic print is of a

subject requiring the use of instruments it should be securely

fastened to a drawing board, square with the board, so that any

horizontal and vertical lines in it may be ruled by the use of a =T=

square and triangle. For specimen or landscape work it need not be

fastened.

For bleaching blue prints a saturated solution of oxalate of potassium

(K2C2O4 + H2O) has been used with good results. For bleaching bromide

prints cyanide of potassium (KCN) to which a few drops or flakes of

iodine have been added should be used. Neither kind of print should be

bleached until the drawing has been completely finished in every

detail, because bleaching loosens the fibers of the paper, so that the

ink of any added lines is likely to spread. The print should be placed

in a hard-rubber pan, the bleaching solution poured on it, and the pan

rocked until the image disappears. The print should then be carefully

removed, thoroughly washed in running water, placed between clean

white blotters to dry, and finally mounted on cardboard. For

temporary, hurried work on drawings that are not to be retained for

future use the blue print may be mounted first and bleached by pouring

the bleaching fluid over the mounted print.

BRUSH DRAWINGS FROM POOR PHOTOGRAPHS.

Brush drawings may be made directly from photographs by working over

an enlarged print with gouache, or by making a pencil tracing and

sketch of the photograph and working it up with lampblack or india

ink. The photograph should be larger than publication size to permit

greater freedom and breadth in drawing details. The larger size will

also afford a more refined and better engraving when reduced. If

lampblack or india ink is used and the subject is small, bristol board

is recommended, but if the photograph is larger than, say, 8 by 10

inches, Whatman's hot-pressed double elephant or similar paper, laid

down with thumb tacks, will prove satisfactory.

If gouache is used over a print a preliminary drawing is of course

unnecessary, but the photograph should be an unglazed print of a size

that will require considerable reduction, and the finished drawing

should be protected by an oversheet. If lampblack or india ink and not

gouache is used the photograph should be traced and a fairly complete

pencil sketch should be made before the brush is used.

Plates I, IV, _A_, V, _B_, and VII, _B_, Monograph 34, were made from

gouache drawings. Plates III, _A_, VII, _A_, X, XI, XII, XIII, XX,

XXVIII, and XXX, in the same publication, were made from lampblack or

india-ink wash drawings. The originals can be examined at any time.

OUTDOOR SKETCHES.

The art of sketching from nature is one in which few but professional

artists excel. Not many geologists are able to make sketches from

nature that are suitable for direct reproduction. An artistic

draftsman should be able to redraw the geologist's sketches, however,

in their true perspective and relations, with the skill necessary to

make them satisfactory illustrations.

In most crude outdoor sketches the important features are usually

shown with sufficient clearness to follow. If they are not the

draftsman should ascertain what those features are and prepare the new

drawing in such a way as to display them properly. The new drawing

should be made with pen and ink, generally for reduction to a text

figure, which is the most appropriate form for such an illustration.

In all sketches of this kind the lines should be drawn in such a way

as to produce natural effects and at the same time to make good

printing plates. Good examples of pen and ink sketches of this class

can be found in Monograph 34, already referred to, and in the Seventh

Annual Report, especially Plates XXVIII and XXXVIII; Ninth Annual

Report, Plates XLIII and XLIV; Tenth Annual Report, Plates XIV and XIX

and figure 58; Eleventh Annual Report, Plates XV, XXVII, XXXV, LII,

and LIV and figures 18, 30, 31, 67, 98, and 99.

DRAWINGS OF CRYSTALS.

A crystal should generally be drawn in outline with straight lines.

The invisible rear side of a crystal, if shown, should be represented

by dashed lines. The outer boundary line of a crystal should be

slightly heavier than the inside lines, which should all be of the

same weight. Striations should be shown by straight lines; broken or

uneven surfaces by irregular lines. A twinning line, if an

intersection edge, should be solid; if not an intersection edge it

should be broken into dashes. Italic, Greek, German, and Old English

letters are used to mark crystal faces. All faces of a given form

should be marked by the same letter but may be differentiated, if

necessary, by primes or numerals, thus: m, m', m'', m''', m{'v}.

"Leaders" should be short full lines, or, if these are likely to be

confusing, they should be dashes. Numbers may be used in place of

letters for specific purposes. Letters indicating twin faces are

underscored; a second twin is doubly underscored or overscored, thus:

m_, m=, m¯. Twin units may be differentiated by the use of roman

numerals.

RETOUCHING PHOTOGRAPHS.

An author, of course, selects his photographs to illustrate some

special features; he does not always consider their fitness for

reproduction. Photographs that are blurred or out of focus, those in

which the shadows are too black or lack transparency, and those which

have local defects, such as bad skies or spots, must be worked over to

make them suitable for reproduction. In order to remedy these defects

and produce natural results the draftsman doing work of this sort

should be able to see and interpret nature properly and to supply

natural effects in a manner corresponding with those produced

photographically. He should be sufficiently expert with the brush and

pencil and in handling an air brush to duplicate the delicate and soft

tones in the photograph, and he should know how the pigments he uses

will "take" when the subject is reproduced.

The retoucher should have access to an air brush and should provide

himself with a jar of photo white or blanc d'argent and a color box

containing indian red, crimson lake, yellow ocher, lampblack, and

ultramarine--colors with which he can duplicate those shown in any

photograph. He should also have the best grade of red sable brushes,

ranging in size from No. 3 to No. 8, a stack of porcelain saucers, and

a jar of oxgall. By mixing the colors to match exactly the shades of a

photograph and using a red sable brush he can strengthen details,

"spot out" flaws, and remove imperfections, except those in skies or

other large, flat areas, for which he must use an air brush.

The air brush has become a necessary adjunct to a retoucher's outfit.

Smooth, even gradations of flat tones can not be successfully applied

to photographs without it, and it is therefore indispensable,

especially for retouching skies and covering other large areas.

Before retouching a photograph the draftsman should mix in a saucer a

tint that will match the color of the part that is to be retouched and

should try this tint and note its effect after it has dried and change

it, if necessary, until it matches the color exactly. If he is to

retouch a number of photographs that have the same local color he may

with advantage make up enough of the tint for the entire lot,

thoroughly mixing it and seeing that it is not too thin. In making

this tint he should use only pigments of the best grade, and if he

finds that the Chinese or other white he is using does not photograph

well, or that it does not hold its color, he should discard it at once

and use another brand. Photographs that are to be retouched should be

large enough to permit sufficient reduction to soften the effects of

retouching.

In order to eliminate the lines of junction between two or more

photographs that are joined together to form a panorama some

adjustment or fitting of details by retouching is generally required

before the group is rephotographed to obtain a new print of the whole

on one piece of paper. As it is often desirable to increase the width

of such an illustration the photographer should be instructed to print

the photograph on a strip of paper that is wider than the negative, so

that, if necessary, the retouching may be carried above or below the

new print to add depth to the illustration.

Panoramas may also be drawn from photographs with either pen or brush

in the manner described on pages 68-69.

PART III. PROCESSES OF REPRODUCING ILLUSTRATIONS.

METHODS EMPLOYED.

The preliminary work in producing illustrations includes the

preparation, from originals submitted by authors, of drawings and

other kinds of "copy" in such a way that the copy can be reproduced in

multiple by printing.

Several processes are used for preparing plates for printing

illustrations, and each has its peculiar features of excellence. One

process may render fine details with facility but may fail in

uniformity in large editions; another may be cheap and effective on

the whole but may not reproduce fine details; and still another may

give fine color or tone effects but may be too expensive. Therefore a

knowledge of the varied uses and results and of the cost of the

several processes of reproduction and, on the other hand, of the kinds

of originals that are best suited for reproduction by any one of the

processes is essential to effectiveness and economy in planning,

preparing, and reproducing an illustration.

The following condensed descriptions of processes are intended mainly

to aid in determining the kind of copy that is appropriate for each

process and the kind and quality of reproduction to be expected, so

that only the principal operations or stages in each process are

described. Wood engraving, which was used in making printing plates

for many of the illustrations in the early publications of the

Geological Survey, is described here only to compare that laborious

and "indirect" method of engraving cuts with the more modern kinds of

relief engraving. In 1892 it gave way to photo-engraving.

PHOTO-ENGRAVING.

GENERAL FEATURES

The term "photo-engraving" is applied to processes by which a black

and white line drawing, photograph, or like original is reproduced in

relief on a metal plate from which prints may be made on an ordinary

printing press, in distinction from processes that print from flat or

relatively flat surfaces, such as the lithographic and photogelatin

processes. The photo-engraving processes that are most generally used

are those called "zinc etching" and "half-tone engraving." These

processes depend on the discovery that gelatin or similar organic

material, if treated with potassium or ammonium bichromate and exposed

to the action of light, is made insoluble in water. If a metal plate

coated with bichromatized gelatin or albumen is exposed to light under

a negative the parts acted upon by light become insoluble and those

not acted upon remain unchanged and may be washed away so as to expose

the metal, which is then etched with acid in order to give relief to

the unexposed parts and make of them a printing surface.

ZINC ETCHING.

Zinc etching is adapted to the direct reproduction of a pen and ink

drawing composed of lines, dots, or solid black areas. On the finished

metal plate these lines, dots, and solid areas form the printing

surface, and the spaces between them, which have been etched away,

represent the white or blank parts of the picture. The process is

cheap and is almost universally used for reproducing small drawings

designed for text illustrations. It is also well adapted to the

reproduction of maps and diagrams measuring in print not more than

about 10 by 14 inches. One of the chief advantages of this and of all

other direct (photographic) processes of engraving is that they

reproduce a drawing in facsimile, whereas the "personal equation" must

enter into all engravings made by an indirect method--that is, by

hand--such as wood engraving, wax engraving, and engraving on stone or

copper, which make it necessary to compare every detail of the proof

with every detail of the drawing before the engraving can be approved.

The pen drawing to be reproduced, which should preferably be

considerably larger than the completed engraving, is first

photographed to the proper size or scale on an ordinary negative film.

The film is then stripped from the negative and reversed in order that

the etched plate may print the design as in the original and that the

film may be grouped with other films on one large glass and all

printed at the same time. The negative (whether a single film or

several) is then placed in a specially constructed printing frame in

contact under pressure with a sensitized zinc plate and exposed to

light.

After the zinc plate has been removed from the printing frame (in the

dark room) the plate is rolled with printer's transfer ink, which

resists acid, and placed in a shallow tray containing water, in which

it is rocked for several minutes, and then taken out and rubbed gently

with cotton. The parts of the coating of the plate that were acted on

by light have become insoluble and will therefore be unaffected by the

water, but the parts of the coating not acted on by light and

therefore not hardened will be removed by the washing, which will

expose the metal and leave the parts acted on by light--the

picture--in black lines, dots, etc. The plate is then dusted with

"topping powder," a resinous substance which adheres only to the parts

carrying the ink. The plate is then heated so that the resin and the

ink that remain fuse together and form, when cooled, a resistant

surface which will not be affected by the acid to be used later in

etching the unprotected parts of the plate.

The plate is now ready for a preliminary etching in a fluid consisting

of water and a few drops of nitric acid. It is placed in a tray,

rocked gently for a short time, and then removed, washed well in

running water, drained, and dried with gentle heat. "Dragon's blood,"

a resinous powder that resists the action of acid, is next applied to

the plate, in order to protect the sides of the lines and the dots

from the acid, and the plate is then heated just sufficiently to melt

the powder and units it with the ink. A small quantity of nitric acid

is now added to the etching bath, and the plate is subjected to its

first thorough biting or etching. It is then removed from the bath,

washed under a tap, carefully wiped with a damp rag, and dried with

gentle heat.

The plate is thus treated three or more times until it is etched deep

enough to insure satisfactory printing, and it is then ready for

finishing, which consists of deepening the larger open spaces between

the lines with a routing machine and of cutting away with hand gravers

lines that are improperly connected or that are so close together that

they will not print separately. The routing machine is provided with a

cutting tool mounted on a revolving spindle that projects downward

into the engraved plate, which is securely fastened. The movement of

the arm that holds the cutter is universal and can be controlled with

great precision. The plate is then "proved" that is, a proof is taken

from it on paper and if the proof is satisfactory the plate is nailed

to a block of wood on which it will be "type high" (0.918 inch), for

printing.

Most drawings for zinc etching are made with a pen in black ink and

consist of lines, dots, or masses of black, but drawings may also be

prepared by using some medium that will produce a fine stipple, such

as a black crayon on rough paper or Ross's stipple paper. (See p. 24.)

The drawing should be one and one-half to two or three times as large

as the printed illustration, for it is impossible to obtain a

satisfactory reproduction of a pen and ink drawing without some

reduction. If the drawing has not been reduced the lines appear

heavier in the reproduction than in the drawing, and imperfections

thus become more noticeable; if it has been properly reduced,

imperfections are diminished and the lines and dots become thinner and

finer than those in the drawing. In making a drawing that is to be

reduced the draftsman can also space his lines farther apart and work

out his details more easily.

An author should carefully examine and approve the finished drawings,

which can, of course, be greatly altered, if necessary, before they

are engraved; but similar corrections can not be made on proof sheets

of zinc cuts, which should not be marked for alterations except by

eliminating parts. Minor changes can be made in such a cut by an

expert "finisher," but if the cut is small it is generally cheaper to

correct the drawing and have a new cut made.

Zinc etchings cost about 10 to 25 cents a square inch, the cost being

varied according to a standard scale which is based upon the

ascertained cost of reproduction. The minimum charge for a single cut

is $2.

COPPER ETCHING IN RELIEF.

Copper etching, which produces a line cut in relief, requires the same

kind of copy that is most often marked for zinc etching and is used to

obtain deeper etching and a more permanent cut. It is said to produce

better printing plates than those etched on zinc and is used largely

for reproducing script lettering and other fine work. As copper plates

will hold up longer in printing than zinc, a cut etched on copper may

not need to be electrotyped.

The chemical part of the process is practically the same as that

employed for etching half-tone plates, described under the next

heading.

The cost of etching on copper is considerably greater than the cost of

etching on zinc. This process is not often used in reproducing

illustrations for publications of the Geological Survey.

HALF-TONE ENGRAVING.

The half-tone process is, in name at least, familiar to almost

everyone who has had any connection with the making of books, whether

as author, editor, illustrator, or printer. The invention of a

photomechanical process of reproducing a line drawing to make a metal

plate that could be printed along with type on an ordinary printing

press naturally led to attempts to reproduce similarly a photograph.

It was known that the intermediate shades between white and black in a

photograph--the half tones--can be reproduced on an ordinary printing

press only by breaking them up into dots or lines that will form a

good printing surface and that by their variation in size or density

will give for each shade the effect of a uniform tone. In the

half-tone process this effect is produced by photographing the picture

or object through a screen.

The half-tone screen consists of two plates of glass, on each of which

lines running generally at an angle of 45° to the sides of the plate

have been engraved, cemented together so that the lines cross at

right angles. The lines, which are minute grooves filled with an

opaque black pigment, thus appear as a series of black crossed lines

on a white ground. The screen is placed in the camera in front of the

negative. Screens are made that show from 60 lines to an inch for the

coarser newspaper illustrations to 250 lines or more to the inch for

fine book work. The screens used for magazine illustrations generally

show 120 to 150 lines. Those used for Survey publications show 150 to

175 lines, and for reproducing delicate drawings and photographs of

fossils screens bearing 200 lines to the inch are sometimes specified;

but these finer screens require the use of highly super-coated papers,

some of them made of cheap fiber and not known to be permanent. For a

half tone that is to be printed in the text a 100-line or a 120-line

screen is specified. (See Pl. VI, p. 56.)

The method of etching a half-tone plate does not differ greatly from

that used in zinc etching, and there are several kinds of half-tone

plates, though most of them are etched on copper, not on zinc, those

etched on zinc being used principally for newspaper illustrations. The

half-tone screen is used also in other processes to obtain a negative.

When a half-tone negative hag been made the film is stripped from the

glass plate and reversed, as in the zinc-etching process, though some

half-tone engravers use a mirror box or prism by which the picture is

so disposed on the negative that it does not need stripping and

reversing. A perfectly flat, clean, and highly polished copper plate,

generally large enough to accommodate several such films, is then

coated with a sensitive film according to one of several formulas, all

based on the fact that gelatin or some similar body, if sensitized

with certain chromic salts, becomes hardened and insoluble in water on

exposure to light. This plate is then placed in the printing frame in

contact, under pressure, with the glass negative plate and is exposed

to light in the usual manner. The copper plate is then removed from

the frame in the dark room and made ready for etching.

For etching half-tone plates on copper a saturated solution of

perchloride of iron is used instead of the solution of nitric acid

used for zinc etching. The time of etching ranges from about 5 to 15

minutes, according to the strength of the solution. One etching is

generally sufficient, but it may be necessary to give the plate

another "biting" if it has not been etched deep enough, or to re-etch

it in order to strengthen contrasts. If, for instance, the sky in a

half-tone plate shows too dark or is uneven in tint it can be made

lighter or more even by re-etching. On the other hand, if certain

features on a plate are too light they can be darkened by

burnishing--rubbing the surface with a highly polished steel burnisher

under just sufficient pressure to flatten slightly the fine points

that form the printing surface of the plate. When the plate leaves the

hands of the etcher it is turned over to the finisher, who with a

graver removes spots or any other imperfections that may appear on it.

Sometimes a roulette is used to lighten parts, and other tools are

used for special purposes.

After a plate that shows two or more pictures has been etched and

finished it is divided by sawing them apart. Each one is then put into

a beveling machine, where its edges are trimmed and the usual border

is made, if it is desired. The separate plates are then ready to be

proved and mounted on blocks of wood which make them type high, ready

for printing.

The half-tone process is used almost exclusively for reproducing

photographs and wash drawings, though it will produce a facsimile of

any kind of copy, such as impressions from type, old manuscripts, or

typewriting, but a shade composed of minute black dots will appear

over the entire print and there will be no absolutely whits areas

unless they are produced by routing the plate or cutting out the high

lights. (See p. 74.) The reproduction of an ordinary outdoor

photograph requires very little handwork, except for re-etching,

burnishing, and cutting the borders. In the reproduction of copy that

is made up of separate parts, such as groups of photographs of

specimens that are to appear on a white ground, the half-tone

"tint"--or more properly shade--between and around the several figures

must be removed and numbers must be added. This operation requires two

negatives--one half tone and one line--and produces what is called a

"combination" plate. Therefore the difference in the cost of making a

half-tone cut from a single photograph of a landscape and from a cut

made from "copy" of the same size consisting of a number of small

photographs or drawings, to which numbers or letters are added, is

considerable (about 50 per cent greater) and depends upon the amount

of additional work involved. Routing, when needed, must be done with

extreme care lest the edges of a figure be marred, and this work

requires skill that can be gained only by experience.

Copy for the half-tone process should be as nearly perfect as

possible. Only the best photographs should be selected. Prints on

semimat velox and glossy haloid papers are regarded as the best

photographic copy for reproduction. Every part of the photograph or

drawing should be absolutely clean. If any part that should be pure

white becomes soiled or stained the defects will be reproduced. If a

photograph needs retouching it should be retouched with great care and

just sufficiently to correct defects and to bring out or strengthen

the important details. In many photographs the skies may be "muddy" or

uneven in tone, and this defect can be corrected by the use of an air

brush, the only medium that will produce an almost even tone. As

already stated, half-tone plates can be improved by re-etching and

tooling, but tooling tends to destroy the effects of nature and

produces an artificial appearance in the print. One who is preparing

wash drawings for reproduction by the half-tone process should

remember that brush marks and other inequalities of tone will be

reproduced with as much fidelity as other details. Such drawings

should therefore be made two or three times larger than the engraved

cut in order to subdue all unnatural effects and to soften the general

tones.

Line drawings are not generally suitable copy for the half-tone

process, but it is occasionally desirable to use that process instead

of zinc etching for reproducing a line drawing that has been

inexpertly prepared if the cost of redrawing would more than offset

the difference in cost between zinc etching and the more expensive

half-tone process. In reproducing a pen drawing by half tone the lines

become softened and represent the details and shading only; but the

pen drawing may be further developed by brush work. Examples of this

type of reproduction are Plates V, _A_, VI, _A_, and XV, figure 10,

and other illustrations in Survey Monograph 34.

Vignetting, which consists of a skillful grading off of the edges of a

picture, as well as extensive tooling or hand engraving, is often

employed for artistic effect but should be specified only for

exceptional illustrations. The plates made for the Survey are either

"square trimmed" or the ground tint is entirely omitted or routed

away; they are not usually tooled or vignetted.

Half-tone cuts etched on copper cost 20 to 60 cents a square inch, the

cost being varied according to a standard scale based on the

ascertained cost of reproduction. Those that require a screen finer

than 150 lines cost 25 per cent additional. The minimum charge for a

single cut is $3.

Half tones etched on zinc (100-line screen or coarser) cost 25 per

cent less than those etched on copper.

THREE-COLOR HALF-TONE PROCESS.

The three-color process is practically an adaptation of the half-tone

process to color printing based on the theory that all colors or hues

in nature can be reproduced by combinations of three colors of the

spectrum--red, blue, and yellow. The process differs from the ordinary

half-tone process particularly in the use of color filters in making

the negatives and in the character of screens and diaphragms used.

This process, like all others, is worked somewhat differently in

different establishments. In what is called the indirect method, the

one most commonly used, twelve photographic operations are necessary

to produce one illustration, or the three plates or cuts from which

one illustration is to be reproduced by printing. These twelve

operations produce three chromatic negatives, each representing one

color; three transparencies or positives, made from the chromatic

negatives; three half-tone negatives, made from the positives; and

finally three contact prints, made on sensitized metal plates. In what

is called the direct method the half-tone screen is placed in front of

the photographic plate so that it becomes also a half-tone negative

from which a print is made on a sensitized metal plate. Thus the

photographic operations in the direct method are reduced to six, but

the interference to the passage of light offered by the half-tone

screen and by the prism used to reverse the image on the negative

lengthens the time of exposure.

Unfortunately, no pigments have been found that can reproduce in

purity the colors of the spectrum, and to this fact is due the failure

of the process to reproduce exactly all the colors, tints, and shades

of an original. When a drawing in black on white paper is photographed

only the white paper affects the negative film. The transparent parts

of the developed negative thus represent the black, and the opaque

parts, which have been acted upon by light, represent the whits.

Theoretically, when a chromatic negative is made for the yellow plate

a purple-violet filter cuts out all the yellow and allows the red and

blue rays to affect the plate; when a negative is made for the blue

plate an orange filter similarly cuts out the blue and allows the

yellow and red rays to affect the plate; and when a negative is made

for the red plate a green filter cuts out the red and permits the blue

and yellow rays to affect the plate. These color filters, which are

usually made of transparent stained gelatin, are generally placed in

front of the lens. When printing plates like those used in the

half-tone process have been made from the three negatives and the

plates have been inked with yellow, blue, and red ink, respectively, a

combined impression from them will produce a close approximation of

the subject photographed. The colored inks often used are light

yellow, peacock or prussian blue, and bright, transparent crimson.

The ordinary half-tone screen, which bears lines cut at an angle of

45° to the sides of the plate, is rectangular, but the screens used

for three-color work are made circular in order that they may be

turned in the camera to make the lines intersect at other angles, the

angles being varied to avoid producing an undesirable pattern or a

moire effect. Turning the screen also prevents the exact coincidence

or superposition of the red, blue, and yellow dots, which would

produce black. In other respects the screens do not differ essentially

from those used in ordinary half-tone work.

As special experience is necessary in printing three-color plates the

engraver generally delivers the printed illustrations to the purchaser

instead of the plates, which he furnishes for other kinds of relief

printing.

The copy for this process may consist of anything in color, such as

specimens, objects, paintings, or properly colored photographs. The

process does not usually reproduce all the colors and tints of an

original with equal exactness and is not used by the Survey for work

that demands precise reproduction of color, but it is satisfactory for

reproducing most colored drawings, colored photographs of specimens,

or the specimens themselves if they show individual variations in

color. As the process is entirely photomechanical it gives more

scientific accuracy in detail than chromolithography, in which there

is much hand work, and it is much less expensive. If the colors shown

in proofs are not satisfactory they can be modified.

The four-color process, in which four color plates are used, gives a

closer approximation of true color values than the three-color

process, and at a comparatively small increase of cost. The additional

color used is generally a neutral gray or black.

WAX ENGRAVING (THE CEROTYPE PROCESS).

The wax or cerotype process does not require finished drawings and is

especially suitable for making text illustrations and small maps,

although it may be used also for large work. For this process blue

prints, pencil sketches, old prints, or rough copy of any kind may be

submitted--that is, it is not necessary to furnish carefully prepared

drawings in black ink, as it would be for photo-engraving, for the wax

engraver will reproduce in proper form any illustration in which the

copy and the instructions show what is wanted, just as an experienced

draftsman will make a good drawing from the rough original furnished

by an author. Full and clear instructions should always be given,

however, as to the size of the cut wanted and what it is to show.

In this process a polished copper plate is coated with a film

consisting of beeswax, a whitening medium, and other ingredients, and

the coating, which varies in thickness according to the nature of the

copy, is sensitized as in the ordinary photographic processes. The map

or other design to be engraved is first photographed to publication

size and a contact print is made on the wax coating from the negative.

The lines and other parts of the photographed image are then traced or

cut through the wax to the copper plate with steel tools and

straightened or perfected by the engraver, but the lettering is set in

printer's type, which is pressed into the wax until it also touches

the metal plate. After the work of cutting through the wax has been

completed the larger open spaces between the lines are "built up" by

the addition of wax to give greater depth to the plate, so that the

wax plate thus built up corresponds to an electrotype mold. The plate

is then dusted with powdered graphite and suspended in a solution

containing copper, where by electrolytic action a copper shell is

formed over its surface. When this shell is sufficiently thick it is

removed from the solution and reinforced on the back with metal, and

proofs are taken from it. If the proofs are satisfactory the plate is

blocked type-high.

Wax-engraved plates may be used for printing colored maps or diagrams,

in which variations of tint are produced by various kinds of machine

rulings. The effect of some of the colors thus produced is almost a

"flat" tint, in which a pattern can be detected only by close

scrutiny. Some color work is printed from a wax base plate in

combination with half-tone color plates.

The price of a wax engraving depends entirely on the size of the cut,

the amount of work involved, and the character of the original copy,

but it should not exceed very much the cost of a carefully prepared

pen drawing plus the cost of a zinc etching made from it. Cuts

engraved by the wax process, like zinc and half-tone plates, are

delivered to the purchaser. If colored work is ordered, however, the

printed sheets, not the cuts, are delivered.

WOOD ENGRAVING.

Wood engraving was once the universal method of producing cuts for

illustrations that were designed to be printed on an ordinary press.

It is said to be the oldest of all methods of engraving illustrations.

The engraving is made on a block of boxwood, a very dense, hard wood

of a light-yellow color. The block is cut type-high across the grain,

and the engraving surface is made perfectly smooth by nibbing it with

pumice or other stone. When a cut is to be larger than 3 or 4 inches

square the wood block is made up of pieces securely dovetailed or

joined together to prevent splitting and warping. A woodcut is not

used for printing but is electrotyped and the electrotype is used in

the press.

Originally the smoothed surface of the wood block was coated with

prepared chalk or Chinese whits, and on this coating a finished

drawing was made with a brush and pencil by an illustrator. According

to more recent practice the surface of the wood is covered with a

sensitized coating, on which the drawing or design to be engraved is

photographed. The engraver then, with various kinds of gravers and

other tools, cuts out the parts of the picture that are to be

represented by white paper and leaves the lines, dots, and black areas

as a printing surface, thus translating the shades and tints of the

picture into a system of lines and dots which exactly duplicate, in

effect, the details and tones of the original design. In order to

produce a line effect of an area in which the tone is intermediate

between whits and black the engraver must space his lines so that

one-half the area will remain as printing surface and the other half

as white spaces, and he must give character and direction to his

lines, so that, if he is skillful, he can reproduce not only the

delicate tones but the texture and details of the original picture.

Many wood engravers became noted for their artistic rendering of

magazine illustrations, of famous paintings, and of other works of

art.

The Survey began to abandon this method of engraving in 1884, when the

Sixth Annual Report was in press, substituting for it the cheaper

photomechanical processes, zinc etching and half-tone engraving, and

entirely abandoned its use in 1892.

Many good examples of wood engraving may be found in the early

monographs and annual reports of the Geological Survey. Monograph 2

contains numerous examples.

PHOTOGELATIN PROCESSES.

Bichromatized gelatin is used in several photomechanical processes of

reproducing illustrations, but in the photogelatin processes the

gelatin not only receives the image by exposure to light through a

negative but becomes a printing surface on a plate from which prints

are made somewhat as in lithography. The several photogelatin

processes are much the same as the original collotype process and are

best known by the names collotype, heliotype, albertype, artotype, and

the German name lichtdruck.

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.

[Footnote 11: Kubel, S. J., Lithographic stone: U. S. Geol. Survey

Mineral Resources, 1900, pp. 869-873, 1901.]

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 Statute | Parallel of Statute | Parallel of Statute

latitude. miles. | latitude. miles. | latitude. miles.

----------------------+-----------------------+----------------------

0 69.172 | 31 59.365 | 61 33.623

1 69.162 | 32 58.716 | 62 32.560

2 69.130 | 33 58.071 | 63 31.488

3 69.078 | 34 67.407 | 64 30.406

4 69.005 | 35 66.725 | 65 29.315

5 68.911 | 36 66.027 | 66 28.215

6 68.795 | 37 65.311 | 67 27.106

7 68.660 | 38 64.679 | 68 26.988

8 68.504 | 39 63.829 | 69 24.862

9 68.326 | 40 53.063 | 70 23.729

10 68.129 | 41 62.281 | 71 22.589

11 67.910 | 42 51.483 | 72 21.441

12 67.670 | 43 60.669 | 73 20.287

13 67.410 | 44 49.840 | 74 19.127

14 67.131 | 45 48.995 | 75 17.960

15 66.830 | 46 48.136 | 76 16.788

16 66.510 | 47 47.261 | 77 15.611

17 66.169 | 48 46.372 | 78 14.428

18 65.808 | 49 45.469 | 79 13.242

19 65.427 | 50 44.652 | 80 12.051

20 65.026 | 51 43.621 | 81 10.857

21 64.606 | 52 42.676 | 82 9.659

22 64.166 | 53 41.719 | 83 8.458

23 63.706 | 54 40.749 | 84 7.256

24 63.228 | 55 39.766 | 85 6.049

25 62.729 | 56 38.771 | 86 4.842

26 62.212 | 57 37.764 | 87 3.632

27 61.676 | 58 36.745 | 88 2.422

28 61.122 | 59 35.716 | 89 1.211

29 60.548 | 60 34.674 | 90 .000

30 59.956 | |

_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 Statute

latitude. miles.

----------------------

0 68.704

10 68.725

20 68.786

30 68.879

40 68.993

50 69.115

60 69.230

70 69.324

80 69.386

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 33-1/3 inches and is

computed as representing 2.78 feet.

_Geologic eras, periods, systems, epochs, and series._

Era. Period or system. Epoch or series.

{ { Recent.

{ Quaternary. { Pleistocene (replaces "Glacial").

Cenozoic. {

{ { Pliocene.

{ Tertiary. { Miocene.

{ { Oligocene.

{ { Eocene.

{ { Upper (Gulf may be used

{ { provincially).

{ Cretaceous. { Lower (Comanche and Shasta may be

{ { used provincially).

{

{ { Upper.

Mesozoic. { Jurassic. { Middle.

{ { Lower.

{

{ { Upper.

{ Triassic. { Middle.

{ { Lower.

{ { Permian.

{ { Pennsylvanian (replaces "Upper

{ Carboniferous. { Carboniferous").

{ { Mississippian (replaces "Lower

{ { Carboniferous").

{

{ { Upper.

{ Devonian. { Middle.

{ { Lower.

{

Paleozoic. { Silurian.

{

{ { Upper (Cincinnatian may be used

{ { provincially).

{ Ordovician. { Middle (Mohawkian may be used

{ { provincially).

{ { Lower.

{

{ { Saratogan (or Upper Cambrian).

{ Cambrian. { Acadian (or Middle Cambrian).

{ { Waucoban (or Lower Cambrian).

{ Algonkian. }pre-Cambrian.

Proterozoic. { Archean. }

_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.

[Greek: A] [Greek: a] Alpha. A.

[Greek: B] [Greek: b] Beta. B.

[Greek: G] [Greek: g] Gamma. G.

[Greek: D] [Greek: d] Delta. D.

[Greek: E] [Greek: e] Epsilon. E short.

[Greek: Z] [Greek: z] Zeta. Z.

[Greek: H] [Greek: h] Eta. E long.

[Greek: Th] [Greek: th] Theta. Th.

[Greek: I] [Greek: i] Iota. I.

[Greek: K] [Greek: k] Kappa. K.

[Greek: L] [Greek: l] Lambda. L.

[Greek: M] [Greek: m] Mu. M.

[Greek: N] [Greek: n] Nu. N.

[Greek: X] [Greek: x] Xi. X.

[Greek: O] [Greek: o] Omicron. O short.

[Greek: P] [Greek: p] Pi. P.

[Greek: R] [Greek: r] Rho. R.

[Greek: S] [Greek: s] Sigma. S.

[Greek: T] [Greek: t] Tau. T.

[Greek: U] [Greek: u] Upsilon. U.

[Greek: F] [Greek: f] Phi. F.

[Greek: Ch] [Greek: ch] Chi. Ch.

[Greek: Ps] [Greek: ps] Psi. Ps.

[Greek: Om] [Greek: om] 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. Ironstone (also igneous).

Alabaster. Itacolumite.

Alluvium. Kame.

Alum shale. Kaolin.

Anhydrite. Laterite.

Apron (alluvial). Lignite.

Argillite. Limestone.

Arkose. Limonite.

Asphalt. Loess.

Bench gravel. Marble (also metamorphic).

Bentonite. Marl.

Boulder clay. Metaxite.

Brea. Morainal deposit.

Breccia. Mudstone.

Brownstone. Novaculite.

Burrstone. Peat.

Calcarenite. Pelite.

Calc sinter. Phosphate rock.

Caliche. Phosphorite.

Catlinite. Phthanite.

Chalk. Psammites.

Chert. Psephites.

Clay. Puddingstone.

Coal. Pyroclastic material.

Conglomerate. Quartzite (also metamorphic).

Coprolite. Reddle.

Coquina. Rock salt.

Detritus. Rock stream.

Diatomaceous earth. Rubble.

Diluvium. Salt.

Dolomite. Sand.

Drift. Sandstone.

Fan (alluvial). Selenite.

Fanglomerate. Shale.

Flagstone. Silt.

Flint. Slate (also metamorphic).

Freestone. Soil.

Fuller's earth. Stalactite.

Geyserite. Stalagmite.

Gravel. Talc.

Graywacke. Talus.

Greensand. Till.

Grit. Travertine.

Gumbo. Tripoli.

Gypsum. Tufa (=chemically deposited lime).

Hardpan. Tuff (=igneous fragments).

Hematite. Wacke.

Infusorial earth. Wash.

_Metamorphic material._

Adinole. Hornstone.

Amphibolite. Itabirite.

Andalusite schist (?). Kinzigite.

Apo (rhyolite), etc. Knotenschiefer.

Argillite. Knotty schists.

Augen gneiss (also igneous). Luxulianite (igneous?).

Biotite schist. Marble.

Calc schist. Meta (diabase), etc.

Cataclastic. Mica schist.

Chlorite schist Mylonite.

Clay slate. Ophicalcite.

Damourite schist. Ottrelite schist.

Desmosite. Phyllite.

Dynamometamorphic rock. Porcelanite.

Eclogite. Protogene.

Epidosite. Pyroschists.

Erlan. Quartz.

Erlanfels. Quartzite.

Eulysite. Quartz schist.

Fibrolite schist Schist.

Garnet rock. Sericite schist, etc.

Garnet schist. Serpentine.

Gneiss. Slate.

Granite gneiss. Soapstone.

Graywacke (?). Sodalite.

Green schists. Spilosite.

Greenstone (also igneous). Steatite.

Greisen. Talc schist.

Halleflinta. Topazfels.

Hornblende schist Topaz rock.

Hornfels. Zobtenite.

_Igneous material._

Absarokite. Dolerite.

Abyssal. Dunite.

Adamellite. Durbachite.

Adendiorite. Effusive rock.

Ailsyte. Ekerite.

Åkerite. Elvan.

Alaskite. Enstatite.

Albitlte. Eruptive rock.

Allivalite. Essexite.

Allochetite. Estrellite.

Alnölte. Eulysite.

Alsbachite. Extrusive rock.

Ambonite. Farrisite.

Amherstite. Felsite.

Analcitite. Felsophyre.

Andesite. Fergusite.

Anorthosite. Fortunite.

Aphanitite. Fourchite.

Aplite. Foyaite.

Arkite. Gabbro.

Atatschite. Gauteite.

Augen gneiss (also metamorphic). Garewaite.

Augitite. Glumarrite.

Avezacite. Gladkaite.

Banakite. Granite.

Banatite. Granitite.

Bandaite. Granitoid.

Basalt. Granodiorite.

Basanite. Granophyre.

Beerbachite. Greenstone (also metamorphic).

Bekinkinite. Greisen (?).

Bombs. Grorudite.

Borolanite. Harrisite.

Bostonite. Harzburgite.

Camptonite. Haüynophyre.

Carmeloite. Hawaiite.

Cascadite. Hedrumite.

Chibinite. Heumite.

Ciminite. Holyokeite.

Comendite. Hornblendite.

Complementary rocks. Hypabyssal rock.

Coppaelite. Hyperite.

Cortlandite. Hypersthenite.

Cromaltite. Ijolite.

Cumberlandite. Intrusive rock.

Cuselite. Irruptive (=Intrusive) rock.

Dacite. Isenite.

Dellenite. Jacupirangite.

Diabase. Jumillite.

Diallagite. Kaiwekite.

Dike rock. Kedabekite.

Diorite. Kentallenite.

Ditroite. Kenyite.

_Igneous material._--Continued.

Keratophyre. Perlite.

Kersantite. Phanerite.

Kimberlite. Phonolite.

Kobalaite. Pierite.

Krablite. Pitchstone.

Krageröite. Plagiaplite.

Kulaite. Plagioclastic.

Kyschytymite. Plumasite.

Lamprophyre. Plutonic rock.

Latite. Pollenite.

Laugenite. Porphyry.

Laurdalite. Pulaskite.

Laurvikite. Pumice.

Lava. Pyroxenite.

Lestiwarite. Rhombenporphyry.

Leucite basalt. Rhyolite.

Leucite tephrite. Rizzonite.

Leucitite. Rockalite.

Leucocratic. Santorinite.

Lherzolite. Sanukite.

Limbergite. Saxonite.

Lindoite. Scyelite.

Liparite. Shastaite.

Litchfieldite. Shonkinite.

Lithoidite. Shoshonite.

Luciitss. Soda granite.

Lujaurite. Sölvsbergite.

Madrupite. Sommaite.

Maenaite. Spessartite.

Magma basalt. Sussexite.

Malchite. Syenite.

Malignite. Taimyrite.

Mangerite. Tawite.

Mariupolite. Tephrite.

Melaphyre. Teschenite.

Melilite basalt. Theralite.

Mesanite. Tilaite.

Mica peridotite. Tinguaite.

Minette. Tjosite.

Missourite. Tonalite.

Monchiquite. Tonsbergite.

Mondholdeite. Tordrillite.

Monmouthite. Toscanite (?).

Monzonite. Trachy-andesite.

Mugearite. Trachyte.

Naujaite. Trap.

Nelsonite. Troctolite.

Nephelinite. Umptekite.

Nevadite. Unakite.

Nordmarkite. Ungaite.

Norite. Urtite.

Obsidian. Valbellite.

Odinite. Venanzite.

Orbite. Verite.

Orendite. Vitrophyre.

Ornöite. Vogesite.

Orthophyre. Volcanic rock.

Ortlerite. Volhynite.

Ouachitite. Vulsinite.

Paisanite. Websterite.

Pantellerite. Wehrlite.

Pegmatite. Windsorite.

Peridotite. Wyomingite.

Perknite. Yamaskite.

INDEX.

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. 98

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. 04

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

[Illustration: circle]

* * * * *

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