2 BULLETIN 54_, U. S. DEPART ME ISTT OF AGRICULTURE. 



of the deposit if any exists. It can not be said that any one of these 

 questions is more important than the others, since the solution of all 

 will be essential to a full understanding of the greater problem. It is 

 fair to say, however, that the question first named must first be solved. 

 It takes precedence, perhaps, not logically, but chronologically. It 

 is obviously useless to spend time in study of the conditions which 

 may have controlled segregation in a basin to which no potash has 

 been supplied or from which it has escaped. 



The problem, then, is first of aU that of locating those areas in which 

 potash reasonably may be expected to have accumulated and from 

 which it apparently has not been withdrawn. This is not a matter of 

 simple observation. There are only very few of the basins in which 

 deposits of soluble salts are exposed on the surface and may be exam- 

 ined directly. Nearly everywhere the salt bodies indicated on sub- 

 stantial though theoretical grounds have been more or less deeply 

 buried by later deposits. Their character, even their presence or 

 absence, must be inferred from general geological evidences, appar- 

 ently somewhat remote from the point at issue. 



Direct evidence being thus lacking and not easily obtainable, the 

 first question (that of accumulation) becomes essentially one of topo- 

 graphy and of areal geology. It is reasonable to expect that potash 

 will have accumulated in largest quantity in that place where the 

 greatest drainage has been concentrated for the longest time and 

 where the rocks from which that drainage is derived are such as 

 may reasonably be expected to yield potash most largely, easily, and 

 rapidly. The matter may be reduced to three formal criteria: (1) 

 The drainage area of the basin (past as well as present) ; (2) the exist- 

 ence or possibiUty of a present or past overflow (which might have 

 removed the potash) ; (3) the nature of the rocks and soils exposed to 

 the drainage. 



Of these criteria the first two are the most important and both are 

 essentially topographic. It is seldom that the rocks of an area are 

 either entirely potash bearing or entirely the reverse. The study 

 of the areal geology is not only seldom conclusive, but is always 

 laborious and is obviously never necessary unless topographic con- 

 ditions are known to be favorable. The first step of the inquiry is, 

 therefore, the study of the topography of the undraiued regions, and 

 it is this step only which is taken in the present report. The writer 

 here sets out to answer the question "In what basins has potash 

 probably accumulated and been retained in significant amount?" 

 With the no less important matters of segregation and position (es- 

 pecially depth) he is not here concerned. 



The topographic data upon which the report is based have been 

 gathered from many and various sources. Chief and most important 

 are the topographic sheets of the United States Geological Survey, 



