John L. Ridgway

“ The degree of generalization in the geologic and other detail to be shown on a map usually involves a corresponding degree of generalization in its base. Absolutely true generalization means the same degree of omission of detail for each kind of feature. If a base map on a scale of 1 mile to 1 inch, prepared with the usual detail, were placed before a camera and reduced to a scale of 16 miles to 1 inch, the lines representing the smaller tributaries of streams and the smaller water bodies, as well as many other features, would probably be so greatly reduced in length as to be illegible. ”

“ Engineers' and architects' drawings generally do not require preparation for reproduction by any process, but in preparing illustrations for the reports of the Geological Survey reproduction must be fully considered at every step, and each drawing must be made according to the requirements of a certain selected process and gaged for a certain reduction. The draftsman should therefore know how to plan each drawing step by step for an engraved cut, a lithograph, a text figure, or a plate, always with a definite result in view. ”

“ To prepare a drawing that will be in every way suitable for reproduction usually requires experience of a kind not acquired in many other kinds of drafting, such as preparing engineers' or architects' drawings, because the drawings themselves or blue prints made directly from them are the things the engineer or the architect desires. Drawings prepared for reproduction are generally made larger than publication size, and it is therefore necessary to gage each line, letter, or feature for a definite reduction. ”

“ 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 [78] by re-etching and tooling, but tooling tends to destroy the effects of nature and produces an artificial appearance in the print. ”

“ 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. ”

“ A feature worthy of illustration deserves good pictorial expression; if it is of superior scientific interest it should not be represented by an inferior photograph. Fortunately, a good, accurate drawing may be made from a poor photograph, and a photographic view that has only minor defects can be successfully retouched. ”

“ Sufficiency of detail depends largely on focus, stopping down, and timing; brilliancy is the direct result of ample illumination by sun or artificial light, without which a photograph will be dull or "flat" and generally unsatisfactory for reproduction. Bad weather may prevent good field exposures, yet even in bad weather acceptable negatives may be obtained by judicious focusing, stopping down, and timing. If a negative is overexposed it may be full of detail, but flat and too thin to print well. ”

“ The effectiveness of illustrations does not depend entirely on good drawings nor on good reproduction; it may be due in large part to the inherent character of the rough material submitted. If this material is effective or striking the finished illustrations, if well made, will be equally effective and striking. Each step in the making of an illustration—first the preparation of the author's original or rough draft, next the final drawing, and last the reproduction—is closely related to the others, and each is dependent on the others for good results. ”

“ 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. ”

“ The judgment of an author as to the illustrative value of a photograph is likely to be biased by his knowledge of the features that are actually included in the view represented, not all of which may be shown clearly in the photograph ”

“ The cultural features represented on a map include "the works of man"—not only cities, towns, buildings, bridges, railroads, and other roads, but State, county, and other boundary lines—in short, all that part of a three-color base map which is shown in black, the engraved plate for the black being called the culture plate. ”

“ 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 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. ”

“ A consideration of processes of reproduction is essential in the preparation of all illustrations, and the influence or effect of the process to be selected on the methods of preparing a drawing has seemed to warrant the presentation of brief descriptions of the processes usually employed by the Geological Survey. ”

“ 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. ”

“ As drawings of fossils or other specimens are prepared separately and grouped into plates, and as most paleontologists make up their own plates, each in his own way, there is naturally great dissimilarity in methods and in results. Ordinary white or light-gray cardboard should be used, and the figures that are to make up a plate should be arranged as stated above but not securely pasted until the grouping is satisfactory. In trimming each drawing or photograph the author should be careful to leave room at its lower edge for the number. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ Not only is the quality of the reproduction improved by considerable reduction, but the larger scale of the drawing facilitates the plotting of details. It should be remembered, however, that a linear reduction of one-half produces a map only one-fourth the area of the original, and reduction so great may prevent the addition of data, such as an extended note in small letters applying to a small area on the face of a map, which would not be legible when reduced. ”

“ 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. ”

“ Simplicity of subject does not warrant hasty preparation, for an original sketch that has been carelessly drawn and is inaccurate or inconsistent in detail may lead to serious errors. Ruled paper printed especially for platting profiles and cross sections should be used. Curves or graphs made by an author with pencil on blue-lined section paper may be inked by more skillful draftsmen. An author's pencil sketches are usually satisfactory if they indicate plainly the facts to be represented, but they should be prepared with some care as to detail. ”

“ 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. ”

“ Unmounted prints are always preferable for use in making illustrations. A group that is to form a single plate should be placed in an envelope bearing the number of the plate and its title, and each print of the group should bear a corresponding number, written in pencil on its back. The envelope will protect the prints and keep them together, and the numbers will identify them. Red ink should not be used to mark photographs, as it is likely to penetrate the coating or even the fiber of the paper, so that it can not be erased. ”

“ Tables and like matter are not generally satisfactory material from which to prepare drawings. In drawings for diagrams that are to be printed in the text as figures the use of large, solid black bars or of conspicuous areas of solid black is objectionable, because the black is likely to print gray and to appear uneven in tone. Ruled tints or cross lining give better effects. Stereograms should be prepared by an author with especial care, for they represent facts only as the author sees them, and the author's view must be imparted to the draftsman graphically. ”

“ 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. ”