ACTIVITIES 43 



propriated for "geologic maps of the United States" has been 

 nearly $2,500,000. To this there should be added a large 

 part of the "lump-sum" appropriations made to the Survey 

 during 1879- 1888. It seems fair to conclude, therefore, that 

 the geologic surveys proper, exclusive of surveys in Alaska, 

 have cost nearly $9,000,000. 



Investigation of Mineral Deposits. In addition to its sur- 

 veys of selected areas, the Survey makes many investigations 

 and surveys with a view to determining the occurrence and 

 distribution of the deposits of a particular mineral, or the 

 mineral deposits in a particular area. Much of this work that 

 is done on the public lands is a direct incident to the task of 

 classifying or evaluating those lands under the land laws, and 

 this phase of the work will be discussed in a subsequent sec- 

 tion. 



The investigations here considered are thus concerned only 

 with a single class of mineral deposits. Though the Survey's 

 work in Alaska has from the beginning been conducted under 

 appropriations for the "investigation of the mineral resources 

 of Alaska," no specific phrase of that kind has ever been used 

 in appropriation bills covering investigations in the United 

 States, which have been conducted under the general authori- 

 zation for "geologic surveys." Investigations of this type are 

 generally undertaken by the Survey with reference to a de- 

 posit of major importance in a field not yet adequately ex- 

 ploited. The Survey attempts to outline the limits of the area 

 in which occurrences of the deposit may be expected, and to 

 indicate the zones in which the richest deposits are likely to 

 be found and the general conditions to be expected. An in- 

 vestigation of this type is the Survey's work on the oil shales 

 of the Green Bay region. 



The Survey also, when an unusual demand arises for any 

 mineral product, makes a general investigation of the occur- 

 rence of that mineral. Investigations have thus been made 

 of such minerals as monazite, zircon, iridosmine, platinum, 



