EDITORIAL WORK ON GEOLOGIC MAPS. 101 
nietainorphie rocks are also printed in any colors, but of less brilliant 
tints. The water-laid sedimentary rocks are represented according to 
a systematic color scheme whereby the age of the beds may be recog- 
nized by the color used. These colors are more somber than those of 
the igneous rocks and are arranged in somewhat prismatic order, from 
orange at the top to brown at the base. The various systems into 
which the sedimentary rocks are divided according to age (the most 
recent at the top) and the corresponding colors are as follows: 
Quaternary . . _ . Brownish yellow. 
Tertiary Yellow ocher. 
Cretaceous - Olive-green. 
Jurassic Blue-green. 
Triassic : Peacock-blue. 
Carboniferous Blue. 
Devonian Blue-gray. 
Silurian Blue-purple. 
Ordovician Red-purple: 
Cambrian Brick-red. 
Algonkian Brownish red. 
Archean Gray-brown. 
Manuscript maps and other sheets pertaining to a folio, when com- 
pleted by the author, are referred to the section of geologic maps for 
critical examination. The text is referred to the section of strati- 
graphic geology for critical reading, and is then read and prepared 
for the printer by the editor of texts. The maps and sections are 
carefully examined by the editor of geologic maps for errors, discrep- 
ancies, or omissions of any kind. Such errors may consist of either 
incorrect geologic interpretations or errors in drafting. Sometimes 
the geologic boundaries do not conform to the contours as the structure 
sections indicate that they should, or the sections do not accord with 
the map, or areas are colored incorrectly. Such errors can be detected 
only by one acquainted with geologic processes. 
After the map is carefully examined from a geologic point of view 
it is scanned by a draftsman, who corrects imperfections in the draw- 
ing. This map, from which the engraving is to be made, must not be 
| colored, as the application of color would distort the paper, and the 
engraving made from it would not fit the topographic base as it should. 
The colored geologic map, which is made for the editor's use only, is 
prepared on a photograph or other copy of the original map. The 
boundaries and faults and the mine, dip, and letter symbols are then 
engraved on the copper plate and proof is read in this section. In the 
plate-proof reading great care is taken to avoid omissions and other 
errors, as it is much easier to make corrections on the plate than on 
l the stone, and the results of changes on the stone are usually not 
satisfactory and may necessitate the retransfer of the map. The 
legend is prepared and engraved separately and often requires much 
