Davis.] 116 [November 1, 



18. For the changes made in the original numbering in my 

 manuscript, for the alleged confounding of the labels of the hand- 

 specimens and for all entanglement eventually ensuing therefrom, 

 of course I am not responsible. 



If, now, we set aside all of these cases, wherein Mr. Wads- 

 worth's accusations are based upon his own arbitrary and indi- 

 vidual terminology in petrography, or upon his improved doctrines 

 about the connection of rocks with one another through process 

 of alteration, or upon his misunderstandings and his unacquain- 

 tance with the facts and events — what remains ? The reproach of 

 my having said, in two instances, that quartz and biotite were 

 absent, whereas Mr. Wads worth found them to be present. 1 If 

 this reproach be well founded, which, at present, I can neither 

 contest, nor grant, I may indeed experience a certain degree of 

 satisfaction in the fact that such unessential points are the only 

 ones in which Mr. Wadsworth has a right to correct me, after his 

 examination of my studies made upon nine hundred and four- 

 teen thin sections. If my decided adversary himself could not 

 detect more weighty errors, I think that I may accept his paper 

 as an involuntary testimonial to the correctness of my long and 

 arduous investigations. 



University of Leipzig, June, 1882. 



THE STRUCTURAL VALUE OF THE TRAP RIDGES OF THE 

 CONNECTICUT VALLEY. 



BY WILLIAM MOKBIS DAVIS. 



The following article is the substance of a paper read before the Har- 

 vard Natural History Society, Oct. 17, 1882. It summarizes the method of 

 study as well as results of a vacation's work on the Triassic formation. 

 Full details of observations and a more extended historic account and dis- 

 cussion of the subject will appear in the Bulletin of the Museum of Com- 

 parative Zoology, Cambridge, Vol. vn ; (geol. series, Vol. I.) 



On our Atlantic slope, there are several long, narrow patches 

 of sandstones and shales of a prevailing red or gray color, and 

 more or less interrupted by ridges of trap rock. It is now gen- 

 ii must deny having mistaken a greenish altered groundmass for olivine. 



