360 Review of the New York Geological Reports. 



Here we have a striking example of one of the grand negative 

 truths of geological science — one, the vast practical utility of 

 which, because of a passive character, and because it merely fur- 

 nishes experience to save the expenditure of immense sums of 

 money and labor, without amassing wealth, is but little appre- 

 ciated. 



West of Little Falls some fine cabinet specimens of copper 

 pyrites have been procured in blasting the rock for the coal. It 

 yields the finest quartz crystals known. Sulphate of barytes is 

 also found in it at the west end of Little Falls. Many of the 

 warm springs of the United States have their origin, according 

 to Vanuxem, at the bottom of the calciferous sandrock. 



This formation seems to have a great range, extending in a N. 



W 



R 



Reports,) including the Chazy, Birdseye, and Mohawk lime- 

 stone, viz. those rocks which form cliffs on Black Rirer from its 

 head to its mouth. 



The lower part, or Chazy limestone of Emmons, is a dark, 

 thick-bedded limestone, from thirty to one hundred feet thick, 

 characterized by the Maclurea, pi. 73, fig. 1, closely allied to 

 Euomphalus, a Trochus, and Columnaria sulcata, (fig. 2.) 



Above this lies a dove-colored limestone about ten feet thick, 

 everywhere distinguished by its peculiar fossil— the so-called 

 Fucoides demissus, (fig. 4, next page,) now considered by Dr. E. 

 to belong to the Polyparia, on account of its internal structure 



pe 



e hanging stem 



The tail of a trilobite (PI. 73, fig. 3) was also found in the 



» 



uiraseye limestone; also Orthoceras multicameratum mdtiwp 

 solites ? 



The Birdseye limestone passes upwards into a dark limestone 

 which affords at Isle LaMotte a beautiful marble. 



On the Mohawk the upper layers, or transition to the Trenton 

 limestone, have an interlamination of shale, and contain the re- 

 mains of large Orthoceras, the Actinoceras of Bigsby and Diplo- 

 ceras of Conrad ; also Strophomena alternata and Cyathophyll^ 

 like ceratites, Columnaria sulcata. 



The middle portion, or Birdseye limestone, is the most constant 

 in its character, and affords generally a fine rock for construction 

 and the manufacture of pure lime. 



