78 ulrich: major causes of oscillations 



wider range of geological data and criteria than any other specialist 

 in the science ? Of them all, I regard the stratigraphical paleon- 

 tologist the best equipped to bring out the dominant facts in 

 questions of the kind before us. He has the same opportuni- 

 ties and desire to observe and note the phsyical factors of the 

 problem, and in addition an appreciation of organic criteria 

 that may not only be applied directly in the field but the tangible 

 evidence — in the form of specimens usually small enough to be 

 collected — may be carried to the laboratory and there be studied 

 at leisure and as often as desired. I have found this of very 

 great advantage. 



For such reasons I would be disposed to prejudice in favor of 

 earth students like Vaughan or Schuchert in cases of contro- 

 versy with others who can not personally take into account and 

 weigh the organic as well as the physical aspects of a problem. 

 However, in the present instance, I have gathered so much com- 

 petent evidence of my own that I feel warranted in reaching the 

 conviction that the major factors in the control and migration 

 of the strandline lie and have always lain in deformative move- 

 ments within the lithosphere. These movements, whether large 

 or small and whether due to shrinkage of the centrosphere, to 

 local changes in crustal density, to unequal loading by rock or 

 ice, or to erosion and further lightening of positive areas, are all 

 primarily concerned with the maintenance of isostasy. 



