mS The American Geologist. Deci'mber, isie 
se(|uenc'e. tliat it luus Ijccii found cousistt'ut with eeonomy to 
abandon the four-inikvto-the-inch scaU', and isul)sequently thi' 
t\vo-mile-to-tho-inch scale was abandoned also. Tiiis adoi)tion 
of tlie one-mile-to-the-inch scale was also RMulcred necessary, as 
it l)ecame evident that the rec^uirements of geologists would not 
1)6 met satisfactorily b}' the smaller scales. The total area sur- 
veyed topographically to date is 537.000 sciuare miles, distributed 
over 42 states and territories. Four states, viz.. Connecticut. 
Massachusetts, Xew Jersey and Rhode Island, together with the 
District of Columbia, have been completed. Each sheet of the 
maps is about 15 x IH in. and the side of the one-mile-to-the-inch 
map represents 15 minutes of latitude. The sheets are engraved 
on copper and are printed from stone transfers. Each sheet is 
printed from three plates, giving respectively the hydrography' in 
blue, the altitudes l)etvveen contour lines in shades of l)rown, and 
the topography in black. Altogether tU 5 sheets are now printed 
in the different scales out of the (IIU sheets surveyed for. No 
legal provision has yet been maile for the j)ul)lic sale of these 
maps. 
No system has ever yet been uniformly adopted among civilized 
countries for representing the geological structure and character- 
istics in maps. Most geological authorities at present adopt some 
arbitrary systeni of coloring according to their own taste and 
fancy, so that the art of geological mapping may be said to be only 
in an experimental stage as yet The system adopted by the U. S. 
Geological Survey is novel, and is thought to meet the require- 
ments of engineers, miners, etc., in a better way than any other 
method yet proposed or tried. The system provides for the separ- 
ation of rock formations into four classes, viz. ; 1. Fossiliferous 
or fragmental; 2, volcanic; 3, granitoidal and schistoidal, and 4, 
superficial. These classes of rocks are represented by ground 
colors and pattern overprints in such a manner that the entire 
range of available colors may Ije used f(^r each. The fragmental 
rocks are represented by the primary colors in orderly arrange- 
ment, each color indicating an age-group (Carboniferous, Silurian, 
etc.). These colors are used as uniform ground tints, and oA'cr- 
prints iji line patterns represent the distinct formations of which 
the group is made up. The volcanic rocks are represented by 
angular figures either on a white ground or over a groimd tint 
representing an age-group. The crystalline rocks are similarly 
