U. S. GEOLOGICAL SURVEYPREPARATION OF ILLUSTRATIONS. PLATE III.Click on image to view larger size.LITHOLOGIC SYMBOLS USED IN STRUCTURE AND COLUMNAR SECTIONS TO REPRESENT DIFFERENT KINDS OF ROCK
U. S. GEOLOGICAL SURVEY
PREPARATION OF ILLUSTRATIONS. PLATE III.
Click on image to view larger size.
LITHOLOGIC SYMBOLS USED IN STRUCTURE AND COLUMNAR SECTIONS TO REPRESENT DIFFERENT KINDS OF ROCK
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.
If a print is of doubtful quality two copies of it should be submitted—one glazed, the other having a dead finish or "mat" surface, which is generally preferable if the print must be considerably retouched. The best prints for use as illustrations are those made on "regular" or "special" semimat velox and glossy haloid papers. The author should indicate prints that may be grouped together according to their relation geographically or by subject. Generally two half tones will be combined on a page, and the list of illustrations should be prepared accordingly.
With slight trimming and reduction, three photographs measuring 31/4by 51/2inches may be made up one above the other to form a full-page octavo plate. Four photographs in which the longer dimensions represent vertical distances may sometimes be used if they are placed sidewise on the page, with side titles.
Some photographs may be reduced to the width of a page by trimming instead of by photographic reduction, which may involve loss of detail. The author should clearly indicate the extent of such trimming as they may bear without loss of essential details. The trimming is best done during the final preparation. A line should not be drawn across a photograph to mark such trimming, but the position of the line or lines should be indicated either on temporary mounts, on the backs of the prints, or by a statement, such as "One inch may be cut off on right, one-fourth inch on left, and one-half inch at bottom."
COPYRIGHTED PHOTOGRAPHS.
Section 4965 (ch. 3, title 60) of the Revised Statutes, amended by act of March 2, 1895 (Stat. L., vol. 28, p. 965), provides that no copyrighted photograph may be used without the consent of theproprietor of the copyright in writing signed in the presence of two witnesses. A penalty of $1 is imposed for every sheet on which such a photograph is reproduced without consents, "either printing, printed, copied, published, imported, or exposed for sale." An author should therefore obtain the written consent of the owner of a copyrighted photograph to use it, and the letter giving this consent should be submitted with the illustration.
SOURCES OF PHOTOGRAPHS.
Every photograph submitted with a manuscript should bear a memorandum giving the name of the photographer or the owner of the negative. If the negative is in the Survey's collection that fact should be stated, as "Neg. Keith 318." The Survey receives many requests for copies of photographs that have been reproduced as illustrations in its publications, and replies to these requests will be facilitated if the Survey's number or the source of each photograph presented for use as an illustration is stated as above on the photograph.
LENDING ORIGINAL PHOTOGRAPHS AND DRAWINGS.
A photograph that has been used in making a half-tone cut for a Survey report can not be lent, but if the negative is on file a print can be furnished at cost; and a Survey drawing that is well preserved can be photographed and a print furnished, also at cost. Requests for such prints should be addressed to the Director.
UNPUBLISHED PHOTOGRAPHS.
The Survey can not issue a copy of an unpublished photograph except upon the written approval or requisition of the person under whose name the negative is filed. This requirement does not apply to a print needed for official use, nor to a print made from an old negative reserved under the name of any present member of the Survey or from a negative that has been released by the person under whose name it is filed.
Authors using Survey photographs in unofficial publications are requested to acknowledge the source of the photograph by adding to the printed title such a statement as "Photograph by U. S. Geological Survey (David Whits)."
SPECIMENS.
GENERAL REQUIREMENTS.
Specimens other than fossils that are to be illustrated in a report should be photographed before they are submitted, but the requisition for the photographs should be initialed by the chief illustrator, who will indicate the kinds of prints needed. Duplicate photographs of the specimens should be made up into temporary plates by theauthor and submitted with his other illustrations, the specimens being retained subject to call, if needed, when the illustrations are finally prepared. Should a colored illustration of a specimen be needed, however, the specimen must be submitted with the report, and a different kind of print, preferably one made on platinum or other special paper, will be obtained by the section of illustrations.
BORROWED AND FRAGILE SPECIMENS.
In submitting specimens to be illustrated an author should call attention to those that have been borrowed and to those that are fragile. Borrowed specimens will receive first attention, so that they may be returned promptly.
TRANSMITTAL OF PALEONTOLOGIC SPECIMENS.
All requests for paleontologic illustrations should be addressed to the Director. The letter of transmittal should state the title of the paper, the form of publication desired (bulletin, professional paper, or monograph), and the status of the manuscript, whether completed or in preparation. If the paper is unfinished an estimate of the number of illustrations required should be given, and the special reasons for prompt preparation should be fully stated. A letter transmitting a second or third lot of fossils should refer to the preceding lot or lots if all the fossils are to be used in illustrating the same paper.
Fossils that are to be drawn should be sent directly to the section of illustrations, but those that are to be photographed and require unusual posing or that are extremely delicate and valuable may be sent directly to the photographic laboratory to avoid repeated handling. Each specimen or, if it is very small, each box or bottle containing a specimen should be numbered, and each lot should be accompanied by a list giving their names and numbers. Full instructions as to size of reproduction, together with sketches showing the point of view preferred and any special features to be displayed should also be submitted. All specimens that show strong colors and all groups of specimens that are not uniform in color will be coated by holding them in the vapor of ammonium chloride unless directions to the contrary are given by the author of the paper. As it may not be desirable to apply this process to soft or fragile specimens or to specimens that have been borrowed an author should indicate any specimens that may not be so treated. Specimens whose color aids in revealing detail are not so coated. If any features of a specimen are unusual that fact should be stated so that the photographer and the retoucher may perform their work according to the requirements.
MAKING UP PLATES.
Two or more illustrations may be combined to form one plate in order to permit easy and close comparison as well as for economy, for if a particular illustration is too small to make a full plate and is not suitable for enlargement other illustrations that are closely related to it may be put on the same plate. The size of the printed page as given in the table onpage 11will determine the size of the plate.
In making up plates composed of a number of figures the author should endeavor to group related figures together and at the same time to observe proper regard for artistic effect, but as figures vary in size and shape a grouping according to relations may not be possible in some plates. If related figures can not be kept together the larger and darker figures should be placed in the lower part of the plate and the smaller and lighter above. If a plate consists of one large figure and several smaller ones the large figure should be placed below and the smaller figures above.
A number designating a figure should be placed immediately below the figure, and a series of such numbers should preferably begin with 1 in the upper left corner and continue consecutively across and down through the plate. This arrangement is not always possible, however, on account of variations in the size of figures.
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. Small drawings or photographs, such as paleontologists use, when pasted on bristol board or other board faced with tough paper are difficult or impossible to remove without injury if they have to be remounted; figures pasted on ordinary white or gray cardboard can be removed without difficulty. Each plate should be made up in a size to fit the volume or in its correct proportion to a page in the volume in which it is to be used (see table onp. 11), and each figure should be properly oriented—that is, all vertical lines, or the vertical axis of each specimen, should be parallel with the sides of the plate. When the figures are being mounted care should be taken that the mucilage or paste does not exude under pressure and cover any part of the drawing or photograph. The same attention should be given to pasting on numbers. Inattention to these details may produce results that will affect the reproduction of the plates.
Ordinary mucilage may be used for mounting drawings and photographs, but photo paste gives good results and is perhaps cleaner to handle. Dry-mounting tissue is well adapted to mounting single illustrations but not groups of figures. Liquid rubber is sometimes used, but it is not suitable for mounting small figures, such as drawings and photographs of fossils. It can be used satisfactorily for mounting temporary plates and for mounting photographs in albums and on large cards for study or exhibition; but it has not proved to be a permanent adhesive. Its special merit is that it does not cause either the photograph or the mounting sheet to warp. It is applied by spreading it evenly over the back of the photograph with the fingers. The superfluous rubber can easily be removed from the hands and from the cards or sheets when it is dry. Anything mounted with liquid rubber can be easily removed.
If a plate is to be made up of a small number of figures that require different reductions, the author, instead of mounting or pasting the separate figures on one card in the manner already indicated, may draw a rectangle of the size of the printed plate and sketch within it the several figures in their respective sizes and positions. These "dummy" plates or layouts should be numbered as plates, and they may bear captions and titles. The photographs or drawings represented by the sketches should then be numbered to identify them with the sketches on the dummy plate, and those that pertain to each plate should be inclosed in an envelope attached to the dummy plate. A plate made up in this manner will meet every requirement of the photo-engraver or lithographer.
If a paleontologist so desires, his plates can be permanently made up after he has transmitted his material, but he should always submit a tentative arrangement.
REUSE OF ILLUSTRATIONS.
If an author desires to use in modified form an illustration already published, whether by the Geological Survey or by an outside publisher, he should furnish a print or tracing of the illustration showing the changes desired. If the illustration is not to be modified he need only give the title of the volume in which it was used, with the number of the page, figure, or plate, and he need not make a sketch of the illustration or furnish a dummy; but its title should be quoted and proper reference should be given in the list of illustrations. Due credit should be given to the author or publisher.
The original cuts of illustrations will be kept for one year after the report for which they were made has been published, and authors of later reports may and should reuse, whenever practicable, any such cut that will serve as an illustration. In the author's list of illustrationssuch a cut should be referred to by its number as plate or figure and the volume in which it was first used.
An electrotype of any cut on hand will be furnished for use in publications other than those of the Geological Survey at the cost of making, which is 31/2to 51/2cents a square inch of printing surface. The minimum charge for a single electrotype ranges from 46 to 60 cents.
APPROVAL OF FINISHED ILLUSTRATIONS.
After the drawings for a report have been prepared they will be submitted to the author or to the chief of his branch or division for examination. The finished drawings will be accompanied by the "originals," with which the author should carefully and thoroughly compare them. After making a thorough comparison he should mark lightly with a pencil, on the finished drawings, all necessary corrections, or indicate his approval subject to such corrections and additions as may be required. He should verify all type matter and other lettering and assure himself that no mistakes have been made in grouping the photographs into plates, especially such as have been regrouped since they left his hands. The author's list of illustrations will be submitted with the new drawings for this purpose.
REVISION OF ILLUSTRATIONS.
All illustrations receive editorial revision before they are sent to the engravers. After they are drawn they are examined with reference to their scientific features and their accuracy, and then in turn with reference to the correctness of geologic names and geographic names and to errors in statement and in spelling. Each illustration thus, before it is completed, receives critical examination by persons qualified in particular kinds of work to detect errors or omissions.
SUBMITTAL OF PROOFS.
The first proofs of all illustrations are submitted to an author when he is within reach, but if he is in the field and the transmittal of the proofs to him is likely to cause too much delay they are submitted to the chief of the branch or division in which the report was prepared. Second proofs of the more complicated illustrations, particularly geologic maps, may be submitted. An author's examination should be confined principally to the revision of the scientific features of his illustrations, but suggestions as to general effectiveness are always acceptable.
The process to be used in engraving each illustration is stamped in its lower left corner. In examining proofs an author should note the following facts:
1. Changes can not be made in zinc etchings except by eliminating parts, cutting away defects, and connecting lines. If additions arerequired reengraving is generally necessary, and reengraving should preferably be avoided.
2. Changes can be made in half-tone plates only by re-etching certain parts to make them lighter and by burnishing certain parts to make them darker. If the proof shows a general loss of detail the fault may lie either in the proving of the cut or in the reproduction. If it is in the reproduction it can not be remedied without reengraving. A slight loss of detail may be expected in all half tones, especially in those that are smaller than the copy submitted.
3. Minor changes can be made in photolithographs and chromolithographs, but changes can not be made twice in one place without danger of affecting the printing. It is customary to approve all lithographic proofs subject to the corrections indicated, the printed edition being examined and compared, but if the changes are numerous and radical second proofs may be required. Second combined proofs of chromolithographs are very expensive. (Seep. 89.)
PROOF READING ILLUSTRATIONS.
An author should examine the proofs of his illustrations closely and should compare them carefully with the original drawings. A mere cursory examination may fail to detect errors that have not been caught by the regular proof reader. Every correction desired should be clearly indicated with pen and ink in the body of the proof and inclosed in a loop from which a line should be carried to a marginal note or comment, but if the time available is short a pencil may be used. In correcting type matter or lettering (such as that in a geologic legend or explanation) the ordinary proof reader's marks should be used. The author or the person examining the proofs should initial each one at the place indicated by a rubber stamp.
Proofs should be held only long enough to examine them properly and to compare them with the original illustrations, for a time limit is fixed in each contract for engraving, and if the author holds proofs beyond a reasonable time he causes a delay in the fulfillment of the contract.
As the illustrations for many reports contain important data that will be discussed in the text, proofs of illustrations can not be supplied to any applicant without consent from the Director's office.
GENERAL CONSIDERATIONS.
The following requirements are essential to obtain good original illustrations:
1. The material selected should be pertinent and expressive; it should have the qualities essential to good illustrations.
2. The character of the report and the size of the illustrations should be kept clearly in mind. If the report is preliminary or ephemeral the illustrations should be simple and inexpensive. If the report represents the sum of knowledge on the subject treated or the last word on some particular area the illustrations may be more elaborate. The character of a report generally determines the form of publication, which, in turn, determines the size of the pages and the size of the plates and figures. Every sketch made should be larger than publication size—preferably twice publication size—whether it is a simple diagram or a base map.
3. The kind of reproduction that is apparently needed should be fully considered, for it should have some relation to the kind of report. The illustrations for short-lived reports are reproduced by the cheaper processes. Those for hurried reports are reproduced by processes that can be worked quickly, but no process should be considered that will not give a clear reproduction of essential details.
4. Clearness of preparation of original matter is invariably essential. An author should not expect the draftsmen or the editors to supply missing links. Each original should be complete and should be so made that it can be understood and followed without question. Changes made in the finished drawings or on proof sheets are expensive and delay publication.
Part II. Preparation By Draftsmen.
GENERAL DIRECTIONS.
The work of preparing illustrations such as are used in the reports of the Geological Survey is essentially that of making finished drawings from more or less crude and imperfect material furnished by authors to illustrate certain features or phenomena discussed in their manuscripts. Each finished drawing must be so prepared that it can be reproduced in multiple by one of several processes of engraving. The author's sketches and other material are commonly called "originals"; the finished illustrations are known by the engravers as "copy." Though most engraver's copy consists of more or less elaborate drawings that are to be reproduced in facsimile by "direct" processes without the interposition of handwork, some of it consists of more roughly prepared copy which is accurate in statement but requires complete manual or "indirect" reproduction. The direct processes in use are zinc etching, half-tone engraving, photolithography, three-color half tone, photogravure, and photogelatin. The manual or indirect processes are wax engraving, wood engraving, engraving on copper and on stone, plain lithography, and chromolithography. These processes are described on pages 72-90.
Part I of this pamphlet contains some matter that is pertinent to final preparation and should be consulted by draftsmen.
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. 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. He should be familiar with processes of engraving and should know the special requirementsof each process, and he should be able to prepare drawings for any specified reduction in a way to insure good, legible reproduction.
The geologic draftsman should read and study such textbooks of geology as those of Dana and Geikie and should familiarize himself with structural geology, the geologic time divisions, and geologic nomenclature. He should be able to prepare a simple, effective illustration from complicated rough originals and to supply minor missing essential parts or features. To perform his work successfully he must possess mechanical skill and some artistic taste, as well as good eyesight and great patience.
INSTRUMENTS.
The following list of draftsmen's instruments is practically complete. Those which are considered indispensable are marked by asterisks; the others may be used according to individual preference. The same kind of instrument may be duplicated in different sizes according to the variation in the demands of the work.
CLASSIFICATION OF MATERIAL.
The draftsman handling the drawings and other original material submitted by the author of a report for its illustration should first group them, as far as possible, into kinds or classes, in order thathe may decide how each illustration should be prepared (1) to express most effectively the author's purpose, (2) to insure reasonable economy in preparation and in reproduction, and (3) to meet the requirements of the processes of reproduction selected. All similar illustrations for one publication should be prepared in the same general style. In a series of geologic sections, for example, the same lithologic symbols should be used throughout for the same kinds of rocks. The titles, explanations, and captions of the maps should also agree with one another in general style and in details of workmanship.
The draftsman should determine in advance the reduction for each drawing or for each group of drawings, in order that he may use the same size of letters or the same kinds of type for the lettering on a series of drawings that require the same reduction. The reduction should preferably be marked in fractions (as "1/2off," "1/4off" or "reduce1/2," "reduce1/4"), and the choice of the same reduction for a group of drawings will not only insure greater uniformity in the drafting and in the reproduction but will permit the drawings to be reproduced more economically, for the engraver can photograph them in groups instead of each one separately.
The draftsman should therefore note and consider (1) the special features shown in the author's originals; (2) whether or not these features have been plainly indicated and whether the originals are complete; (3) the size of the printed page of the volume in which the illustrations will appear and the reduction required for each drawing; and (4) the process by which each drawing should be reproduced. If an original is of doubtful or uncertain interpretation or appears to be incomplete the draftsman should confer with the author of the paper if he is within reach or should bring the matter to the attention of the chief of the branch; otherwise he may waste much time in making the drawing.
PREPARATION OF MAPS.
PROJECTION.
The base maps furnished by authors (see pp.13-14) are prepared in many different ways and in different degrees of refinement and of crudity, but the work of redrawing them for reproduction involves well-established and generally uniform principles. All maps except those of very extensive areas should be based on a map projection which will show with a minimum of distortion the effect of the curvature of the earth. The polyconic projection (seefig. 5) is used for most Government maps. In this projection the central meridian is a straight vertical line, and each parallel of latitude is developed independently of the others. The mathematical elements of map projectionare given in tables published by the Geological Survey[6]and the Coast and Geodetic Survey.[7]Figure 5, however, illustrates the mechanical or constructional features of the polyconic projection and if used in connection with the published tables will probably be a sufficient guide for projecting a map on any desired scale.
[6]Gannett, S. S., Geographic tables and formulas, 4th ed.: U. S. Geol. Survey Bull. 650, 1916. See also Gannett, Henry, Manual of topographic methods: U. S. Geol. Survey Bull. 307, pp. 85-86, 1906.
[6]Gannett, S. S., Geographic tables and formulas, 4th ed.: U. S. Geol. Survey Bull. 650, 1916. See also Gannett, Henry, Manual of topographic methods: U. S. Geol. Survey Bull. 307, pp. 85-86, 1906.
[7]Methods and results: Tables for the projection of maps and polyconic development; Appendix No. 6, Report for 1884; Tables for a polyconic projection of maps, based upon Clarke's reference spheroid of 1886; 3d ed., 1910.
[7]Methods and results: Tables for the projection of maps and polyconic development; Appendix No. 6, Report for 1884; Tables for a polyconic projection of maps, based upon Clarke's reference spheroid of 1886; 3d ed., 1910.
Figure 5.—Diagram illustrating method of projecting a map.
In projecting a map first select a convenient measuring scale for setting off the dimensions given in the tables, or if no scale is at hand one may be constructed. Measuring scales are made, however, bearing divisions for miles and kilometers and finer subdivisions of 6 to 100 parts. They include the ratios of 1:31,250, 1:31,680, 1:48,000, 1:62,500, 1:63,360, 1:125,000, 1:250,000, 1:500,000, 1:1,000,000, and others. On a map drawn on the scale of 1 to 63,360, for example, 1 inch would represent 1 mile; on a map drawn on the scale of 1 to 1,000,000, 1 millimeter would represent 1 kilometer, and so on. It will be seen that the use of a scale that shows in ratios, such as those just given, the actual distance on the ground as compared with the unit representing the same distance on the map will reduce the possibility of error.
The method of projecting a map, illustrated in the accompanying diagram (fig. 5), is as follows: First draw a straight vertical line (A) through the middle of the sheet to represent the central meridianof the map and a line (B) at the lower end of this line exactly at right angles to it to represent the bottom of the map. Then set off on the line showing the central meridian the distances between parallels given in Table 6 on page 36 of "Geographic tables and formulas" (Bull. 650). It should be noted that the figures in these tables give the distance, in meters and statute miles, of 1° on a meridian measured 30' each way from a point where the meridian is intersected by a parallel. The exact distances between parallels as measured on the ground are given in the Coast and Geodetic Survey tables, or they may be computed from Table 6 of "Geographic tables and formulas" by adding the sum of the figures given for any two latitudes 1° apart and dividing by 2.
The distance between parallels that are 2° apart, as shown in the diagram, may be computed from Table 6 of "Geographic tables and formulas," as follows:
The distances given in the diagram were obtained by adding the figures given in the Coast and Geodetic Survey tables, which yield the same results. Other tables in Bulletin 650 give the true distances in inches on maps of certain standard scales.
Through the points thus obtained on the central meridian draw lines at right angles to the vertical line. Along these horizontal lines lay off the dimensions in the column headed X, Table 6 (pp. 39-47) of "Geographic tables and formulas" as required for each individual map—in the diagram every alternate degree. Draw vertical lines at these points and set off the distance Y in the same table in a similar manner, and the points so found will be the points of intersection of the respective meridians and parallels. Figures are given on the diagram for the thirty-fifth parallel only.
DETAILS OF BASE MAPS.
Anyone who attempts to draw a base map must, first of all, know how each feature or part of the map should be represented. Most of the conventional symbols for features shown on base maps are well established and should invariably be used; for instance, a line composed of alternate long and short dashes (not dashes and dots) represents a county boundary, and a line or two parallel lines across which short lines are drawn at regular intervals represents a railroad. If he finds that two or more symbols have been widely used to representthe same feature the draftsman should select the one that is best suited to the map in hand. The correct forms of the conventional symbols or features to be used in preparing miscellaneous maps are shown inPlate IV, but the size and weight of each line or symbol must depend on the size and character of the map.
TRANSFERRING OF COPYING.
TRACING.
The oldest method of transferring a map or parts of a map or other drawing to another sheet is that of copying it by means of tracing paper. This method, though still used for simple work, has given way to quicker and more effective methods. By one of these methods a piece of thin, fairly smooth paper (not necessarily transparent) is coated with graphite by rubbing over it a soft pencil. When the graphite has been evenly distributed over it, this sheet is laid upon the drawing paper, coated side down, the map or other subject to be copied is laid upon the graphite-coated sheet, and the two outer sheets—the drawing paper and the map—are securely fastened together. By a steel tracing point or very hard pencil the lines and other details of the matter to be copied are then firmly and carefully traced and thus transferred to the clean drawing paper beneath.
For maps that show several features in different colors sheets rubbed with blue, orange, brown, or green pencils may be used, one after another, for tracing each set of the features. Red should not be used, as it is not easily erased. This method insures distinctive lines for the separate features and prevents the confusion that might result from the use of one color only. Exact register of the features shown in the several colors used may be insured by fastening one edge of the drawing to be copied to the drawing paper by mucilage or thumb tacks. The colored sheets may then be slipped in and out without altering the position of the lines or symbols for one set of data with relation to those for the others.
In the final preparation of a base map to be engraved and printed in colors—for example, black, blue, and brown—tracings of the three colors appearing on the original base should generally be transferred, as described above, to one sheet of paper and thus worked up into a three-colored map. It is usually unnecessary and undesirable to draw each color on a separate sheet. The preparation of separate drawings may facilitate reproduction, but if they are made on tracing cloth the usual uneven shrinking or stretching of the cloth may produce misregister in the printing; therefore it is safer to make a single drawing, so that the photolithographer can make three negatives andseparate the colors by painting out or "opaquing" the colors not wanted on each negative. A map drawn on a single sheet is also less bulky and can therefore be more conveniently handled and compared with proof.
If for any reason separate tracings for the different colors to be used on a map are considered desirable they should be made on linen cut from one roll and in the same direction according to the warp and woof.
CELLULOID TRANSFERRING.
In the celluloid method of transferring a map or parts of a map to paper upon which a complete new map is to be drawn the map or part of the map to be copied is photographed to the exact scale of the new drawing and reproduced in graphite on thin sheets of celluloid.
The celluloid sheet is then laid face down in the correct position on the drawing paper and firmly rubbed on the back with a steel burnisher, which makes a perfect offset of the map on the paper. After the parts desired are inked over the rest of the graphite print is easily erased with an ordinary rubber.
By using this method it is possible to get absolute scale and more satisfactory results than by tracing over a photographic print line for line or by using a pantograph.
Requisitions for celluloid prints are made on the form used for requesting photolithographic work.
SKETCHING BY RETICULATION.
If the sheet bearing the design or matter to be copied may be marred without objection it is ruled lightly into pencil squares of equal size. Corresponding squares of the same size, larger, or smaller, according to the size of the new drawing, are then ruled on the drawing paper, and the work is sketched square by square. If the original sheet may not be marred the same result can be obtained by drawing the lines on a transparent oversheet. This method is serviceable for enlarging or reducing simple work that includes no great amount of detail; if great precision of detail is required the original should be enlarged or reduced by photography or by the pantograph.
THE "SHADOWLESS DRAFTING TABLE."
One of the most useful contrivances that has been made for tracing a drawing on the same scale is called by its manufacturers the "shadowless drafting table." The essential features of this table are a wooden box inclosing strong incandescent lights and bearing a ground-glass top. A drawing placed on the ground glass can be soilluminated as to make its lines conspicuous and readily traceable even through relatively thick paper. The table is particularly useful for tracing sheets upon, which the lines are indistinct and would not be discernible under tracing paper with reflected light. It is also useful in preparing drawings in which certain features must register perfectly over each other. In fact any drawing that does not require enlarging or reducing can be traced with great facility by the use of this drafting table, and it is particularly useful for tracing faint lines on old and poorly preserved prints or drawings.
Such a table has been installed in the section of illustrations, where it can be used by authors and others.
TOPOGRAPHIC FEATURES.
RELIEF.
The effect of relief is expressed on a map by three methods—by contours, by hachures, and by shading. (Seefig. 6.) The first method does not give pronounced pictorial expression of relief, though it gives correct shape and exact elevation; the others are mow pictorial, but they do not give exact elevation.
Contours.—As contoured maps are originally prepared from actual surveys the draftsman should simply follow the copy furnished by the topographer or such original matter as may be given to him for redrawing. If the area mapped is large and the contours are close together the original may be transferred by celluloid tracing (seep. 47), or it may be transferred by tracing with graphite-coated paper (seep. 46). After the contour lines have been transferred they should be traced in ink, in lines of even thickness, except those that represent certain fixed intervals and are to be numbered, which should be made slightly thicker. (Seefig. 6, A.) In drawing these lines some draftsmen use an ordinary ruling pen, others the swivel pen; but considerable practice is required in the use of either before it can be controlled to follow precisely the penciled lines. Still other draftsmen use the Shepard pen or an ordinary drawing pen. The swivel pen, if expertly handled, produces a firm and even line.
Italic numbers should be used to indicate the elevation of a contour and should be placed in an opening in the line, never between lines. Where the lines run close together great care should be taken that they do not touch unless the interspaces are so narrow that they must touch and combine. The lines should be firm and even, and if the copy or original map shows that they are uniformly very close together it should be enlarged before the tracing is made in order to give more freedom in drawing; but if the enlarged map is to be much reduced care should be taken to make the lines proportionate to the reduction. A photo-engraving of a map on which the contourlines are drawn very close together is likely to be unsatisfactory because, though the spaces between the lines are reduced in width, the lines themselves may show no corresponding reduction in thickness.
Figure 6.—Methods of expressing relief: (A) by contour lines, (B) by hachures, (C) by shading on stipple board, and (D) by a brush drawing. The four examples given represent the same area. The drawings were made twice the size of the printed cuts.
Certain contour lines are commonly accentuated on a map, generally every fourth or fifth line—that is, for a 10-foot interval every 50-foot line, for a 20-foot interval every 100-foot line, for a 25-footinterval every 100-foot line, for a 50-foot interval every 250-foot line, and for a 100-foot interval every 500-foot line.
Hachuring.—The effect of relief can be produced satisfactorily by hachuring but only by a draftsman who has had considerable well-directed practice in that kind of drawing. In a hachured map the light should seem to come from the west or northwest—that is, the darker parts should be on the east or southeast side of an elevation and the lighter parts on the west or northwest The highest elevation should be represented by the darkest shade on the right and by a corresponding high light on the left. The hachuring should begin at the crest of a peak, range, or butte and be worked downward toward the gentler slopes, the lines being drawn farther apart and made thinner until the floor of the valley is reached and the effect of shadow is lost by fewer and lighter lines. On a hachured map that is made from a contoured map somewhat definite differences of elevation may be indicated by the intervals between the strokes, and abrupt changes in slope may be indicated by shorter and heavier lines. The strokes should be disjointed, and they should trend at right angles to the upper margin of a cliff and should radiate from a peak.Figure 6, B, represents satisfactory hachuring.
Hill shading.—Relief is more easily expressed by shading than by hachuring. (Seefig. 6, C, D.) The draftsman can best express it by this means after he has studied contoured maps or photographs of the region mapped, if they are available, in order that he may obtain an idea of the details of its topography.
The special means used to produce hill shading will depend on the character of surface of the paper on which the drawing is to be made, the size of the map, the amount of detail and refinement of execution desired, and the amount of reduction to be made in reproducing the drawing. For maps on which it is desired to show some refinement of drawing and detail, a lithographic or wax crayon can be used on paper which has a grained surface. The draftsman must express relief according to the information he has at hand, whether detailed or general, and must employ methods that accord with the purpose of the map and the mode of reproduction selected. If a shaded relief map is to be prepared for direct reproduction by photolithography and the shading is to be printed in a separate color the base map should be completed first and a light photographic or blue print obtained on which to add the relief in black lithographic crayon, to insure perfect fitting of the relief and the base; or the relief can be prepared on an oversheet—a semitransparent white paper with sufficient "tooth" or grain to cut the shading up into minute dots. The shadowless drafting table (seep. 47) is especially useful for this purpose. On this oversheet registermarks should be placed at the four comers and at several other points, particularly at the intersection of parallels and meridians.
For relief shading on small black and white maps Ross's hand-stipple drawing paper may be used. (Seep. 24.) By rubbing a black wax crayon or pencil over the surface of the paper the desired effect is produced in fine dots or in stipple, which may be varied in density of shade at the will of the draftsman. (Seefig. 6, C.) High lights can be produced by scraping away the chalky surface of the paper. A lithographic or wax crayon is the best medium to use on this stipple paper, as on the paper referred to in the preceding paragraph, for the shading produced by it is not so easily smeared as that produced in pastel or by a graphite pencil. The object of using either the rough paper or Boss's stipple paper for drawings that are to be reproduced by photo-engraving is to produce a shading that is broken up into dots of varying sizes, which is essential in such reproduction.
Belief shading for maps can also be made with a brush in flat washes of either india ink or lampblack. Such shading should be made only over a blue print or an impression of some kind from the map upon which the shading or relief is to be overprinted. If the relief is expressed on the author's original by contours the general shapes of the relief and the drainage lines can be traced and transferred lightly in blue lines to form a base on which to model the shading and at the same time to make the shading fit the streams. Such a drawing can be photographed through a screen and reproduced by half tone (seefig. 6, D) or mezzotint as a separate plate made to overprint the map in another color.
HYDROGRAPHY.
General directions.—The drainage features of a map should be so drawn as to suggest the natural courses of the streams. Streams should not be drawn in straight, hard lines, as such lines are decidedly unnatural and produce a crude effect. The course of a river may be straight in general, but it is likely to be somewhat sinuous in detail. If the streams shown on a preliminary map are drawn in a clumsy or characterless fashion they should be redrawn with a freehand effect or made slightly wavy, in order that they may appear more natural. The gradual widening of streams from source to mouth should also be shown in the drawing. On small-scale maps, where the eye can at once see a stream through its full length, this almost imperceptible widening can be expressed by a line of almost uniform weight except for the stretch near the source, where it should grow thinner and taper off. On maps which are to be reproduced directly from drawings in black and white and which are to showboth contour lines and drainage the lines representing the streams and other water bodies should generally be drawn freehand and slightly heavier than the contour lines, which should be sharper and more precise.
The names of all streams or other bodies of water should be in italic letters, those of the larger streams being lettered in capitals and those of the smaller streams in capitals and lower-case letters. (See "Lettering,"p. 53.)
Water lining.—The use of water lining on black and white maps should be limited to maps on which the water areas are not readily distinguishable from the land areas. In rough drawings that are to serve only as copy for engravers a flat color may be used for water areas and its conversion into water lines specified. In base maps to be reproduced in three colors a light-blue tint may be used in lieu of water lining, and it can be printed either flat or in a fine ruling transferred to the stone that is to print the drainage. The engraving of water lines is expensive, and the flat blue color should generally be preferred.
Water lining usually consists of 30 to 45 lines on engraved or large maps, but on small maps and sketch maps the number may be reduced as desired. Care should be taken that the lines are as nearly parallel as they can be made freehand and of even weight or thickness. The first three to six lines outside the coast line should be somewhat closer together than those farther out and should conform closely to the coast line, but the spacing between the lines should increase and the lines should become almost imperceptibly less conformable to the coast line as they reach their outer limit, the last three to six being made with the greatest care and refinement. Water-lined maps that are to be reproduced by photographic processes should be drawn at least twice publication size. The reduction will bring the lines closer together, and the reproduction will show a more refined effect than could possibly be produced by the most skillful drawing.
Good examples of water lining, such as are shown on the topographic atlas sheets of the Survey, should be studied by draftsmen before they undertake such work.