170 Jlgricultural Geology of Onondaga County. [April, 



Oriskany sandstone, the materials are all extremely fine; excepting 

 a few thin bands at the superior part of the red marl, composed 

 of coarsish sand. For seven or eight hundred feet then, this pro- 

 perty of the deposit is rather remarkable. The fineness of the 

 material of the rocks, however, is not such as to form an impal- 

 pable soil, it is still suflftciently siliceous and coarse to overcome 

 the adhesive properties of alumine, while the fineness is such 

 as to favor solubility. It is impossible to detect feldspar or mica 

 by the assistance of a microscope in the red or green marls, or in 

 either of the limestones. Their origin cannot be referred to 

 either of the preexisting rocks. All we can say is, that they 

 are the fine sediments which accumulated in the deepest part of 

 an ancient ocean, where organic beings could not probably exist, 

 on account of the gi'eat depth of water. 



The Marcellus shale succeeds the corniferous part of the Onon- 

 daga limestone. We laave now a black rock, the composition of 

 which is not greatly dissimilar to the green shales. This rock is 

 thin bedded and fragile ; and hence the out crop is usually conceal- 

 ed in its own debris. The rock may be known by its position. It 

 is the first rock which contains septaria, a singula): kind of concre- 

 tion of a rounded form ; but it often assumes some imitative shape, 

 as that of a turtle. Sometimes they are globular, and sometimes 

 rounded and flattened, like a cheese. No use has ever been made 

 of the septaria, but there is no doubt they will form an excellent 

 cement. Ten or twelve feet of rough black limestone belongs 

 also to the Marcellus shales. In some places it is called chewed 

 rock, from its ragged surface. This too has a composition which 

 seems to fit it for hydraulic lime. The shales under consideration 

 are composed of the following elements. 



Water,- - - - . 2.00 

 Organic matter, - - - 2.25 



Silex, ----- 48.12 

 Peroxide of iron and alumina, 10.00 

 Carbonate of lime, - - 36.60 



Magnesia, - - - - 1.00 



100.07 



