508 



SEE— ORIGIN OF HIMALAYA MOUNTAINS. [April 18, 



known facts of geodesy as respects the Himalayas are fully ex- 

 plained. And the explanation rests on principles established by a 

 variety of mutually confirmatory observations. 



7. Defects in the Doctrine of Isostacy as Commonly Stated. 



The doctrine of isostacy as commonly stated is vitiated by a 

 serious if not fatal error; and it is necessary to overcome this 

 defect if the doctrine is to hold its place in modern thought. In 

 Science of February 10, 191 1, Professor J. F. Hayford presents a 

 paper based on the valuable data he obtained in the work of the 

 U. S. Coast and Geodetic Survey, deduced from 765 series of astro- 

 nomical observations at 89 stations in the United States. The 

 causes assigned, however, are so inadequate that it seems worth 

 while to point out the defects in his reasoning, which is as follows : 



" Columns A and B have been assumed to contain equal masses. There 

 is complete isostatic compensation. The pressures at the bases of the two 

 columns are equal, and at any less depth, X, the pressure is greater in A than 

 in B. Now assume that in the normal course of events a large amount of 

 material is being eroded from the high surface of column A and deposited 

 on the low surface of column B. After this erosion has been in progress 



SUfJFACE 



OCEAN BOTTOK 



COLUMNi B 



Fig. i 



DEPTH ;< 



DEPTH or COMPCNSATiON 



for some time the isostatic compensation will no longer be perfect. The 

 pressure at the base of B will be greater than at the base of A. The pres- 

 sure very near the top of B will still be less than at the same level in A so 

 long as the top of A remains higher than the top of B. There will be some 

 intermediate level at which the pressure in the two columns is the same. 



