THE MECHANICS OF GEOLOGIC STRUCTURES 523 



folds and actual open ruptures in the tinfoil occurred across some 

 of the folds but were not preserved in the process of casting. 



A rather striking similarity between the folds illustrated in 

 Figure 9 and the structure of the southern Appalachians is appar- 

 ent and the writer ventures to suggest that perhaps certain of the 

 characteristics of the southern Appalachian structure, such as 

 repeated folds, pitching folds, and repeated thrust faults, may 

 receive a certain amount of new light by viewing them with the 

 conditions of the above-described experiment in mind. Whether 

 the deformation was accomplished by straight compression between 

 the oceanic segment and the continental mass or by a shearing 

 movement between these great segments cannot be said. It 

 seems, however, that the latter is rather more probable mechani- 

 cally and that the foregoing experiment demonstrates that the 

 folds of the Appalachians could have been produced by such 

 shearing movement. 



