114 THE UNITED STATES GEOLOGICAL 8UJ8VEY. ' [bull. 227. 
10 hand lithographic presses, stone planer, paper cutter, stitching 
machine, standing press, and a full equipment of tools and instru- 
ments necessary in the work. 
During the present year (1904) expansion of the division is once 
more in progress because of the increased work and appropriation. 
To gain time for proper reorganization and the selection of the addi- 
tional expert workmen necessary, and, in the meantime, to meet 
largely increased demands, it has once more become necessary to have 
the engraving of a small number of topographic atlas sheets done by 
private parties, but in every respect the plates will be uniform with 
those engraved in the office. The expedient is but temporary, and 
it is expected that at the end of a few months the office force will 
again be equal to all demands. 
Copperplate engraving is the fundamental and chief art or process 
employed in reproducing the topographic maps, and to this all the 
others are auxiliary. Though its first cost is greatest, it is the most 
accurate and the only method of reproduction which admits of multi- 
plication by electrotyping. As the topographic atlas sheets are printed 
in three colors — blue, brown and black — representing" respectively 
drainage, relief, and culture features, the engraving must be done in 
part on each of three copper plates. 
The manuscript drawing, which is to be reproduced on the plates, is 
usually in three colors and on a scale somewhat larger than that of the 
engraving. Preliminary to engraving a sheet, a true cop}^ on the scale 
of publication must in some way be transferred to each of the three 
copper plates. There are several methods by which this may be done. 
That formerly in use required that a thin sheet of transparent celluloid 
or gelatine be placed over the drawing — provided it were on the scale 
of publication, otherwise, over a photograph reduced to scale — and 
that an expert trace every line, cutting it into the celluloid or gelatine. 
These lines were tilled with sulphur, and by burnishing, were stained 
on the copperplates. The process was tedious and comparatively 
expensive, and, like all manual work, was subject to errors and 
omissions. 
The process now in use is photomechanical and was devised a few 
years ago by employees of this office. By this process the lines from 
a photographic negative of the manuscript map are stained on the 
copper plates and an absolutely accurate reproduction of the original 
is produced at a cost which is trifling in comparison with hand tracing. 
When the engraving has been completed an impression of each of the 
engraved plates is transferred to a lithographic stone, and from these 
stones the maps are printed. These arts and processes — photograph- 
ing, engraving, lithographing, and printing — are all applied within 
the division. 
