162 



PROCEEDINGS OF COLUMBUS MEETING. 



ically. In Mr. Dale's report to Professor Raphael Pumpelly, United States geolo- 

 gist, dated March, 1890, he described the locality in the following words : 



••East of Great Barrington, at the Searles-Hopkins quarry, a rather coarse-grained muscovite 

 biotite gneiss is in contact with a micaceous pyritiferous dolomite. An analysis of the dolomite is 

 given by Mr. A. A. Julien in his paper on the geoiogy of Great Barrington (Trans-art ions of tin .V u 

 York Academy of Science, vol. v, 1887, page :;7). The plicated stratification planes of the gneiss dip 

 at th'- contact r;n -4(i west, and westerly dips occur also along the steep part of tin.' base Of mount 

 Keith, both north and south of the quarry, hot the gneiss on the hill due south of the reservoir has 

 a stratification dip only a tew degrees east or west of 90°. The cleavage-foliation dip at the quarry 

 is. however. 60° east. The relations of tie' stratification-foliation to the cleavage-foliation are shown 

 in the accompanying sketch, made from a specimen. The general relations of stratification and 

 cleavage in the schists of Berkshire county were set forth in my report on the areal and structural 

 geology of mount Greylock." 



U S.CeOuOClCM. SuRvKY 



SHEFntlt* •S-hEET 



ClTea t square Fool. 



"Plicated Quart* veins and cleavage 

 FoliaCton uxnUiscavite-BiotiXc- 6nfciv5 



near Hof>Kiu% QuanTY, Great .Barri.nqG)n 



1na>-cK imp ' B3 t e 



Figure '■'>. — Cleavagt ami Bi'lnimj near Great Barrington (after Dale). 



The Hopkins-Searles quarry lies very near the line separating the portions of 

 territory allotted to Mr. Dale and myself fur study. Ignorant of the fact that he 

 had examined the locality, I visited it in July, 1890, and arrived at the same con- 

 clusions concerning the general structural relations that he had reached in the 

 previous season. Figure 4 shows the probable relations at the quarry. 4 * 



1 200 



15oloUTi.be Giifcisl,- 



1 1 oo: 



jImc\ ' Spi-in^ 



120 0' 

 -I ioo' 



I oou' 

 _9oo' 



8oo 



8oo' 



Sc.aL^ ["- 5 2 8' 

 Figure 4. — Structure of Hopkins-Searles Quarry. 



* A uniformly easterly cleavage-foliation exists also in the schist west of the Great Barrington 

 valley, where it corresponds more or less closely in direction with the bedding plane. 



