REPORT OF THE DIRECTOR AND STATE GEOLOGIST rl5 



on this scale shows a tract (quadrangle) 15 minutes in extent 

 each way, being one sixteenth of a H square degree or about 

 220 square miles, the area varying with the latitude. An atlas 

 sheet on the second-mentioned or two mile scale is made by the 

 reduction and combination, omitting some details, of four of 

 the mile scale sheets, and represents a tract (quadrangle) 30 

 minutes in extent each way, being one fourth of a " square de- 

 gree ", or about 880 square miles. A few of these have been 

 published. On the annexed map the small rectangles indicate 

 one mile scale sheets. A sheet is designated by the name of 

 some well known place or feature appearing on it. The names 

 of adjoining published sheets are printed on the margins. 



The maps are engraved on copper and printed from stone. 

 The cultural features, such as roads, railroads, cities, towns, 

 houses, etc. as well as the lettering, are in black; all water 

 features, swamps, etc. are in blue; while the hill features are 

 shown by brown contour lines, the contour interval being 20 feet. 



An act of congress prescribes that the maps shall be disposed 

 of by sale. They are accordingly sold at the rate of 5 cents a 

 fcheet. For 100 or more in one order, whether of the same sheet 

 or of different sheets, the price is 2 cents a sheet. All corre- 

 spondence relative to the purchase of maps should be addressed 

 to the Director, United States Geological Survey, Washington 

 D. C. 



Museum work in geology 



In economic geology important progress was made in the re- 

 arrangement of the economic collection and the installation of a 

 large suite of specimens representing the petroleum, salt, talc, 

 garnet, graphite and slate industries of New York. The 

 geographic distribution of each material was, in each exhibition 

 case, illustrated by a small map. 



In historic geology the year's work has been marked by the 

 enlargement of the synoptic collection, among the material con- 

 tributions to which may be enumerated the donation of a series 

 of 19 specimens to illustrate the Carboniferous and sub-Carbon- 

 iferous of Pennsylvania, by Prof. J. J. Stevenson of the Univer- 



