412 



PIONEERS OF SCIENCE IN AMERICA. 



enclosing strata have been submitted, the coal becoming harder 

 and containing less volatile matter as the evidence of disturb- 

 ance increases. 



But the most notable contribution that Prof. Rogers made 

 to the advance of geologic science was the " wave theory " of 

 mountain chains. This was the joint work of William B. and 

 Henry D. Rogers, being founded on their researches in the 

 Appalachian chain, and was presented by them to the Associa- 

 tion of Geologists in 1842 in the form of an oral statement, 

 with the title, The Laws of Structure of the more Disturbed 

 Zones of the Earth's Crust. The theory represented the ele- 

 vation of mountain chains as the result of movements of the 

 earth's surface similar to the movements which raise up waves 

 upon a body of water. The grandeur of the conception, the 

 immense amount of evidence piled up in support of it, and the 

 eloquence with which the whole was presented made a pro- 

 found impression at the meeting. One who was present, Mr. 

 John L. Hays, of Cambridge, said forty years afterward : " I 

 have frequently read it since. To me it is now comparatively 

 tame in expression. It lacks the inspiration of the scene and 

 the man, the illustrative diagrams, the emphasis of voice and 

 finger pointing out the distinguishing phenomena, and the fer- 

 vour of spontaneous utterance. The impression I have of this 

 exposition as delivered is that, next to the Phi Beta Kappa 

 oration of Wendell Phillips at Harvard, it is the most lucid and 

 elegant effort of oral statement to which I ever listened." It 

 was the first important contribution to dynamical and struc- 

 tural geology which had been brought forward in this country. 

 The novelty and importance of its generalizations were at once 

 recognised in Europe as well as at home, and gave the authors, 

 the " Gebriider Rogers," a prominent place among contempo- 

 rary geologists. This memoir is still regarded as of classical 

 value. 



The " wave theory " was further supported by the discover- 

 ies of Prof. Rogers in regard to the distribution of those rup- 

 tures of the strata called faults. He showed in another paper 

 that they do not occur on gentle waves, but on the sharpest 

 flexures of mountain chains, which have given way at the 

 summit where the strain was greatest. Furthermore, the 

 plane of the fault was usually parallel to, if not coincident 

 with, the plane of the ridge. The evidence for this statement 



