S't't Dr. Bigsby's Sketch of the Topography 



sion. It is chiefly visible on the south side of the canal. It 

 appears at Genesee River near Rochester; at Lockport on 

 the canal, and in the great chasm of the Falls of Niagara. Its 

 thickness is variable; from Oneida to Palm3'ra (l^O miles) it 

 is 100 to 250 feet thick, and is fully displayed in this interval. 

 It contains numerous beds of gypsum, and of limestone with 

 shells. As an example of this, Mr. Eaton adduces the neigh- 

 bourhood of Limestone Creek in the township of Manilas. He 

 here " immediately on the ferriferous formation found this 

 slate ; then a bed of gypsum terminating east and west in the 

 bank of the canal, being eight to ten perches in length ; above 

 the gypsum the slate is continued to about the thickness of 

 sixty or seventy feet : then an extensive bed of shell-lime- 

 stone occurs, ten to twelve feet in thickness, and perhaps from 

 half a mile to a mile in breadth; then the slate again, em- 

 bracing a bed of gypsum of much greater extent than that in 

 the immediate bank of the canal. This last-mentioned slate, 

 with its bed of gypsum, terminates the hill upwards." — (G. S. 

 p. 126.) 



The imbedded limestone is in several forms : one, which is 

 dark gray or blue, is perforated everywhere with curvilinear 

 holes, some being still lined with a tubular calcareous crust. 

 The rock in the intervals of holes is very compact. Another 

 common form is siliceous; quartzose and calcareous grains 

 finely comminuted, being all that is essential. It is called 

 " water lime-rock," from its property of hardening under water 

 when used as paste or mortar. In some places it passes into a 

 cellular sponge-like rock, and scarcely contains any carbonate 

 of lime. It then generally abounds in petrifactions. — (P. 127.) 



The calciferous slate is remarkable for its spontaneous and 

 almost universal production of Epsom salts, alum, and copperas. 

 Stalactites of the carbonate of lime, from a quarter to three 

 inches in length, are common on the under surfaces of its thin 

 slaty layers. Vast beds of calc tuff are also produced from it. 



The above account of this rock is wholly that of Mr. Eaton. 

 He also affixes to it a second appellation, "Second grauwacke 

 with shell lime-rock." — I have already objected to this name. 

 Nearly all the rock, as I have seen it at the Genesee Falls, 

 Lockport and Niagara, is strictly an argillo-calcareous shale, 

 in very thin brittle leaves, effervescing freely on exposure to 

 acids; black, homogeneous, of dull lustre, and in places 

 abounding- in fossils characterizing transition limestones*. At 



* Among tliese are two species of Caryocrinites, described by Mr. Say in 

 the 4tli volume of the Journal of the Academy of Natural Sciences of Phila- 

 delphia ; and a very large and remarkable Trilobite, also described in the 

 same vokinie. 



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