42 THE U. S. GEOLOGICAL SURVEY 



tion and thickness of the formations in the area covered, their 

 chemical composition and physical characteristics, and their 

 age— that is, the period of geologic time in which they were 

 deposited, as well as their form— that is, their structure, and 

 the geologic forces which caused their deposition, erosion, and 

 deformation. 



The value of facts regarding the mineral character of rock 

 formations for the development of mineral resources need 

 not be dwelt upon. In disposing of the public lands this in- 

 formation is useful not only in shaping policies but in ad- 

 ministering the land laws, and such information concerning 

 lands privately owned facilitates and expedites the develop- 

 ment of mineral deposits of economic value, or indicates the 

 non-existence of such deposits. In this connection it may also 

 be pointed out that information as to rock formations inci- 

 dentally includes information as to underground water. 



The identification of the geologic positions of several strata 

 in the geologic time-scale is also of value to the economic geol- 

 ogist, as it helps him to determine the probability of the oc- 

 currence, in the area, of particular economic deposits. An- 

 other value, however, lies in the light it throws on the rela- 

 tion of the geology of the area to that of adjacent areas and, 

 ultimately, of the entire country. ^ 



The maps and descriptive texts resulting from geological 

 surveys find a most important use in the hands of the Survey 

 itself in its work of land classification and of geologic re- 

 search. 



It would be difficult to ascertain precisely the total amount 

 spent by the Survey in geologic surveys of the country. The 

 appropriations used have been made under various heads, and 

 some have provided for other work than geological surveys. 

 The total amount appropriated since 1889 for "geologic sur- 

 veys in various portions of the United States" has been about 

 $5,500,000; that appropriated for paleontologic researches 

 (an item of appropriation no longer in use), and for chemical 

 and physical researches has been over $900,000; and that ap- 



