J-^" [Oct. 15, 



"Wallen's ridge and the Clinch river;" and the whole tone of his concluding 

 paragraphs leaves the impression that he assigns the Appalachian flexing 

 to one age and the faults to another and later age. This would be in 

 accordance with his opinions respecting the Pennsylvania anticlinals as 

 preceding some of the coal deposits, published in his Reports of Progress 

 KK and KKK of the Second Geological Survey of Pennsylvania. 



Mr. Lesley said that his long study of the Coal Measures of the United 

 States led him to entertain grave doubts of this. In fact he has repeatedly 

 assigned the regular outspread and remarkably regular increase in the 

 thickness of the Pittsburg coal bed towards the east, over the very large in- 

 terval of country between its Ohio outcrops and its Maryland and Eastern 

 Pennsylvania outcrops, as sufficient evidence that the Appalachian folds 

 had no existence whatever up to the close of the Coal era. 



This extensive study of the faults of Virginia and Tennessee in connec- 

 tion with the unbroken anticlinals of Pennsylvania had in like manner 

 compelled him to see in them one single cause producing essentially the same 

 effect in one and the same age. 



Prof Stevenson postulates the probability of later date for the faults on 

 two classes of observations in Southern Virginia. 



"1. That the course of the streams has not been determined by the 

 lines of fault." 



"2. That erosion along the faulted lines is essentially the same in char- 

 acter and extent with that in localities where no faults exist." 



The second postulate Mr. Lesley considered essentially true, but held it as 

 a proof of the community, not of the non-community of the faults with the 

 other structural features. 



He was obliged, however, to reject the first postulate. On the contrary, the 

 topography illustrated by the maps and sections accompanying his paper on 

 the Coal field of South Virginia, in Montgomery county, and his paper on 

 Scott. Wise and Tazewell counties, Va. (Proc. Anier. Philos. Soc, Vol. IX. 

 page 30, May, 1862, and Vol. XII, page 489, April, 1871) tell nothing more 

 plainly than that the Clinch and other Southern river erosion is wholly and 

 entirelj^and in detail most curiously determined by the faults, in the absence 

 of which the whole water tree of that section of Virginia, and of all Eastern 

 Tennessee would have been of a different character , in other words would 

 have imitated the water-trees of Middle Pennsylvania, where such faults 

 are unknown. 



Mr. Lesley regrelted that Prof Stevenson was not present to explain and' 

 enforce his own views in opposition to this. 



Dr. Barker read a letter from Dr. Henry Draper, of New 

 York, announcing to the Society the first successful photo- 

 graphing of a nebula, the nebula of Orion, by himself, upon 

 the 30th of Septembej'. Dr. Barker expressed his high sat- 

 isfaction that this feat should have been accomplished first 



