No. 3.] BILLINGS — ON THE TACONIC CONTROVERSY. 325 



group, in accordance with Hisinger's list of Swedish rocks as given in 

 his Lethrea Suecia in 1837, and not as lie had previously given it. 

 But the discovery in 1860 of the Point Levis fossils enabled Mr. Bill- 

 ings to prove that the rocks of the Quebejc group must be placed near 

 the base of the Lower Silurian series instead of at its summit, and it 

 thus became necessary to discover some other interpretation of the 

 physical structure than the one suggested by the visible sequence of the 



strata. 



Although there may be difficulties in regard to detail, the interpre- 

 tation given in my letter to Mr. Barrande of the 31st December, 1860, 

 will, I am persuaded, turn out to be the right one. Prof. Emmons long 

 ago asserted that the rocks in question in Vermont were older than 

 the Birdseye and Black River formation. In this I now agree with 

 him ; while however his interpretation of the structure would make 

 them all older than the Potsdam sandstone, mine would not. But 

 whatever the value of my present interpretation, it might have been 

 some time before I should have been urged to look for it, had it not 

 been for the palasontological skill which l\lr. Billings brought to bear 

 .on the question. I am, dear Sirs, very truly and respecfully yours, 



W.E.Logan.' 



To the above I shall add two quotations from the last letter I 

 received from Dr. Emmons on the subject of the Taconic sy^stem. 

 He was, at the date of this letter, State Geologist of N. Carolina : 



" Raleigh, Feb. 5, 1861. 

 Mr. E. Billings : 



" My Dear Sir, — J am much obliged to you for your favor of the 

 30th inst., and especially for the opinions and kind regards which 

 you express. Be assured they are highly appreciated, and the more 

 60 seeing that they are rare. I had for years past looked upon the 

 subject with a kind of indifference, until you had expressed to Col. 

 Jewett, opinions fovourable to the existence of the lower rocks I 

 had contended for ; not indeed that I had any misgivings of the truth 

 of the position I had taken, for that would be impossible from all I 

 had seen, provided there were truth in geology, and that the depart- 

 ment were founded on principles. But the real difficulty has always 

 been that geologists would not look at the question at all." 



" Be assured that I fully appreciate your kind aid in the matter of 

 the Taconic system, for I tliink I should have gone down to the 

 grave before it had been acknowledged, except for your active, intel- 

 ligent, and disinterested labours in the cause." 



" Yours truly, 



•' E. ElIMONa." 



