206 R. Mallet—Origin of the columnar structure of Basalt. 
I regard the Lansingburgh limerock as the stratigraphical 
equivalent of my limestone band No. 1, at Troy. (See this Jour- 
nal for August, 1878.) They are lithologically similar; and, 
moreover, have furnished two species in common, namely, 
C. trilineatus and Hyolithes Americanus. At Troy this deposit 
is similarly underlaid by a heavy slate formation, while appar- 
ently below this, and in the same line of outcrop, there are 
exposed at one point a few layers of thick-bedded sandstone 
similar to that constituting “ Diamond Rock.” The inferior 
tion of the distance, there are almost no expo ‘ 
regular paper relating to the rocks of this district (this Journal, 
is quite possible that these lower sandstones may yet be foun 
to contain a still more ancient fauna. I hope in the coming 
spring, if my opportunities permit, to give this field a more 
careful and extended study. 
Troy, N. ¥., Dec. 26th, 1874. 
Art. XXV.—Abstract of a Memoir on the Origin, and Mechan- 
ism of Production, of the Prismatic or Columnar Structure of 
Basalt; by Ropert Mauer, F.R.S. (Read before the Royal 
Society, January 21st, 1875.)* 
* We are indebted to the author for this abstract.—Eps. 
. 
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