254 T. C. Chamberlin — Jones's Criticism of 



ing wedges implies, of course, that the earth lacks an astheno- 

 sphere or yield zone" (p. 394). 



As if the critical review of a digest of thirteen long arti- 

 cles, the treatment of the five themes of a thesis, and the 

 bringing together in summary form from the various 

 sources of the evidences that support a molten stage and 

 an asthenosphere, afford insufficient scope, the author 

 adds a prophecy of what i ' the study of megadiastrophism 

 is to be " and his interpretation of what that means. The 

 sweep, however, is made wider still; the fundamental 

 issues of the schools are set in array, as follows : 



"This postulate is fundamental. The issue is thus sharply 

 drawn between the two schools of thought. The basic problems 

 of diastrophism, isostasy, and vulcanism must be attacked and 

 interpreted in two diametrically opposite ways by the two 

 schools. The one school, as represented by T. C. and K. T. 

 Chamberlin, interpret these problems from the viewpoint of an 

 earth which has maintained perfect solidity through the forma- 

 tive eras and down to the present The other school, as 



represented by Daly and the late Barrell, interpret these prob- 

 lems from the viewpoint of an earth which passed through a 

 stage of fusion" (pp. 394-5). 



To deal with this frontal screen may be a little tedious 

 but it is necessary to clear the air if any accurate practice 

 is to follow. And first comes the prophecy. Part II of 

 the paper on the "Groundwork" touched upon wedge- 

 dynamics and it is a fair inference that wedge-dynamics 

 will play some part in the superstructure built upon the 

 groundwork and an equally fair inference that it will play 

 the same sort of part that it does in the inquiry cited in 

 the paper. But instead of shaping his forecast critically 

 on these lines, the reviewer introduces a characterization 

 of a radically different sort. The right-minded reader 

 will want to know : 



What are the intimations of ic edge-dynamics as set 

 forth in Part II of the paper on " 'Groundwork." The 

 purpose of Part II was to call attention to the fact that 

 there is available a working method of using the intima- 

 tions of the accessible deformations in determining the 

 downward extension of deformative action, and to bring 

 this extension into service as a part of the start already 

 made in the study of the larger questions of diastrophism. 



