A FRACTURE VALLEY SYSTEM. 



The correspondence between the drainage system in the 

 region north of the Yellowstone National Park and the system of 

 fractures traversing the rocks is so striking that there can be 

 little doubt of a causal relationship between them. The studies 

 of de la Beche in England, of d'Omalius and Daubree in France, 

 of Kjerulf and Brogger in Norway, and recently of Hobbs in 

 Connecticut have demonstrated that in certain localities there is 

 the closest correspondence between the valleys or drainage 

 system and the fractures in the underlying rocks recognized as 

 faults or joints. And Daubree in his classic work Etudes sy7ithi- 

 tiqiies de geologie experinientale , has shown how a more or less rect- 

 angular system of nearly parallel joints may be produced by 

 torsional stress as well as by compression. 



The almost universal application by geologists in former times 

 of the idea of the controlling influence of fractures on drainage, 

 and the exaggeration of the importance of faulting in this con- 

 nection, coupled with the evident independence of many drainage 

 courses from faulting, and their obvious dependence on other 

 factors, led to a revulsion on the part of modern physiographers 

 from the views of earlier geologists to such an extent that the 

 influence of rock fractures on drainage courses has been mini- 

 mized, if not altogether neglected, in recent times. 



One reason for the revulsion from the idea of fracture drain- 

 age systems is to be found undoubtedly in the emphasis formerly 

 laid on the conception of faulting as an essential element in the 

 problem. This was introduced in the term " fault valleys," {I'allees 

 de failles^ of d'Omalius, and has been memorialized in the vignette 

 on the title-page of the Annual Report of the United States Geologi- 

 cal Survey. That such valleys occur is well known, but that they 

 form a small fraction of the whole is beyond dispute. 



It is to be noted, however, that the demonstrations of Daubree 

 deal chiefly with joints or fractures {^cassures^ , rather than with 

 faults [failles), the two being but different phases of the same 



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