ENGRAVING AND PRINTING. 115 
The base of the geologic map is the topographic map. The topo- 
graphic base once engraved, the additional copperplate engraving 
required for the geologic folio is comparatively small. At first it was 
necessary to engrave many plates of designs for color printing. But 
the number of these designs is limited, and, once engraved, the pattern 
plates ma} 7 be used indefinitely by transferring to lithographic stones 
areas to fit an} T required boundaries and printing in any desired colors. 
For the geologic atlas sheet, however, the cultural or black plate of 
the topographic sheet is electrotvped, and upon this electrotype are 
engraved geologic boundaries, symbols, formation letters, and other 
data. The structure sections and columnar sections also are engraved. 
Each folio includes, besides these, descriptive text, which requires the 
application of the typesetting and type-printing art. Therefore, in 
producing a geologic folio, recourse is had to the arts of photography, 
engraving, electro typing, type setting and type printing, stone engrav- 
ing, stone transferring, photolithography, and other similar arts, the 
greatest portion of the work falling upon the lithographic branch. 
At various times different processes have been tried for map repro- 
ducing, but the only important one to become permanent is photo- 
lithography. This is used to great advantage in making available new 
maps prior to their engraving, in publishing maps for special pur- 
poses, in reproducing land plats, and in aiding topographers and 
draftsmen to make reductions and compilations, as well as for many 
other purposes. 
When appointed, the chief engraver was made the custodian of the 
engraved copperplates for 240 topographic atlas sheets, the plates of a 
wall map of the United States, and those of a wall map of Massa- 
chusetts, which had been engraved under the contract system. The 
first of these contracts was awarded to a New York firm for the 
engraving of 100 atlas sheets, in 1881, and during the next five years 
these 240 sheets were engraved. 
The energies of the new division were at first devoted largely to cor- 
recting the plates already engraved, to engraving color-pattern plates, 
and to experimentation for the geologic maps. Though the engrav- 
ing of topographic atlas sheets by contract was continued for five 
years more, the proportion engraved in the office grew rapidly from 
year to year. In the first year of its organization only two atlas sheets 
were engraved in the office; during the third }^ear one-third of all the 
engraving was done in the office; at the end of five years (July 1, 
1894) the last contract had been completed, and since then practically 
all the work has been done in the division. 
In the fiscal year 1889-90 there were engraved by the division 2 topo- 
graphic atlas sheets; ten years later, in 1899-1900, there were engraved 
72 sheets; last year (1902-3), 101. The total number of such plates 
engraved by contractors and office force to date is 1,450. 
