Groundwork for Study of Megadiastrophism. 261 



are usually given by geo-pliysicists in terms of "constants 

 of rigidity,'' and (2) the effects of stresses brought to 

 bear on bodies possessed of this property, which may be 

 as various as the imagination chooses to make them. In 

 considering the effects of stresses of course the time of 

 continuance of the stress is important. But before enter- 

 ing upon discriminations, let us clear away the impres- 

 sion the reader is quite likely to get from the stress laid on 

 the alleged variability, that here is something of import- 

 ance not known to us — and perhaps not to the reader : In 

 the very article under criticism and on the very subject of 

 the relations of the more mobile, more deformed parts 

 of matter undergoing diastrophism to the less mobile, 

 less deformed parts, under conditions of differing depths, 

 E. T. Chamberlin says : 



"No limiting depths can be assigned, for the time-element 

 plays an important part, thongh not easy to evaluate. To quick- 

 acting stresses the earth reacts as an elastico-rigid body ; under 

 long-continued stress it yields to slow movement. With greater 

 depth molecular rearrangement and recrystallization should pre- 

 sumably take precedence" (p. 418). 



Xow the vital question is not what might happen under 

 imagined conditions of stress, but what is the real state of 

 the earth's matter as revealed by three independent lines 

 of evidence interpreted in the light of the stress-conditions , 

 time-conditions, pressure-conditions, temperature-condi- 

 tions, and other conditions that actually exist, in great 

 variety, in the earth. 



This state of the earth substance is what I have empha- 

 sized in my papers. I have referred to the state of the 

 internal matter as elastico-rigid — or some equivalent of 

 this double phrase — with a uniformity and persistency 

 that has made it wearisome to my friends and myself 

 because such reiteration seemed necessary to avoid the 

 ambiguities that cling* about the colloquial term "rigid- 

 ity. ' ' I have tried to use the compound term strictly as 

 a definition of the properties imparted to the matter 

 under consideration by its constitution. I think this is at 

 least not at variance with established scientific usage. At 

 any rate, my use is definite and requires recognition in a 

 critical review, whether approved or not, The important 

 point is to keep clear the distinction between the elastico- 



