R. B. Bashore — Glacial Gravels. 281 



County, which has been briefly described by the writer.* In 

 composition, and in the methods of alteration of feldspar and 

 pyroxene, there is a close resemblance, but a marked difference 

 appears in the fact that the pyroxene of the Pitcairn rock is 

 distinctly older than the feldspar, approaching a prismatic form; 

 and, further, the feldspar is free of inclusions. 



In the ophitic structure, and in the abundant inclusions in 

 the feldspar, the gabbro resembles that of Lake Champlain 

 described by Kemp,f but differs from the latter in the absence 

 of olivine with its attendant reaction rims. 



The Russell rock is much more closely connected with both 

 of these gabbros than with any of the diabases of the region, 

 which, with its extreme coarseness and non-ophitic phases, 

 justifies its classification as a gabbro, rather than as a diabase. 



But it is in its gneissoid phases that the relations of the rock 

 are of most importance, as they may throw some light upon 

 the question of the origin of the Adirondack gneisses. Light 

 colored, granulitic, pyroxene and hornblende gneisses are quite 

 common in the region, and in seeking their origin the possi- 

 bility of their being metamorphosed gabbros was early enter- 

 tained by the writer ; but definite facts bearing upon the ques- 

 tion have been difficult to procure. These gneisses are closely 

 similar to the gneissoid phases of the rock above described, 

 and while this fact affords no proof of the origin of the 

 pyroxene gneisses in general, it is, to say the least, suggestive, 

 and may well help in further investigation. 



Hamilton College, Clinton, N. T., January, 1896. 



Art. XXXIII. — Notes on Glacial Gravels, in the Lower Sus- 

 quehanna Valley ; by Harvey B. Bashore. 



In this Journal for February, 1894, in describing the Har- 

 risburg Terraces, I mentioned that no evidence of flooded-river 

 action had been observed above the highest gravels then 

 reported at that place, i. e. about 130 feet above the river ; and 

 observations since carried on, go far to prove that assertion. 

 It is intended to map out completely the flooded river of gla- 

 cial times from the southern ice limit to tide water, and to 

 obtain all the facts available in regard to the Lafayette, Colum- 

 bia and Trenton gravels in this valley, but the rapid approach 

 of cold weather cut short the work for this season. 



In view of the vast amount of drainage down the Juniatta 

 from glacial Lake Lesley, considerable work was expended at 



* C. H. Smyth, Jr. : Crystalline Limestone and Associated Rocks of the North- 

 western Adirondack Region, Bull. Geol. Soc. Am., 71, p. 263. 



f J. E. Kemp: Gabbros on the Western Shore of Lake Champlain, Bull. G-eol. 

 Soc. Am., v, p. 213. 



