314 



REPORT OF NATIONAL MUSEUM, 1904. 



as great as results from the presence of unstratitied rocks." The 

 actual dolomitization he thought to have been "probably produced by 

 gaseous sublimations, chiefly of carbonate of magnesia, which pene- 

 trated the rock after it had been softened by heat so as to be perme- 

 able/' In some instances, however, he thought it highly probable that 

 magnesian limestone had been deposited directly from thermal waters. 

 In seeking an explanation of the fact that in passing from the top 

 of Hoosac Mountain toward the Hudson River one continually meets 

 newer and newer rocks which always appear to pass under the older — 

 in other words, that there is inversion of the strata — he came to the 

 conclusion, put forward with some hesitation, ""that these rocks have 

 actually been thrown over into an inverted position, or rather, have 

 been so contorted by a force acting laterally that one or more folded 

 axes have been produced." 



The same feature had been mentioned in his report for 1835, but 



then appeared "too im- 

 probable to be admitted." 

 His views on the subject 

 were illustrated by a 

 sketch, copied in fig. 22; 

 the portion above the 

 heavy continuous black 

 line being conceived to 

 have been removed by 

 erosion. Later this ob- 

 servation was claimed to 

 be the first recognition 

 of the true character of 

 overturned folds. This 

 was, however, disputed by H. D. Rogers, who claimed to have made and 

 published similar observations during the progress of the New Jersey 

 survey in 1838-39. 



Below is the paragraph upon which the claim of Rogers was appar- 

 ently based. The statement is made in the course of a description of 

 the various axes of elevation that have given rise to the more promi- 

 nent physical features of northern New Jersey. 



The movement which elevated Jenny Jump, seems to have heen everywhere one 

 of excessive suddenness and violence, as the strata along its anticlinal axis are not 

 only frequently much dislocated and broken, but those lying immediately along its 

 northwestern base are in several places thrown into an inverted posture, dipping not 

 to the northwest, but in toward the base of the hill. & 



«This is probably a reflection of views earlier put forward by Von Buch with ref- 

 erence to the dolomites of the Tyrol. 

 6 Geology of New Jersey, 1840, p. 5o. 



Fig. 22.— Folded axes. (After E. Hitchcock.) 



