268 PALEOZOIC TIME. 



a sketch is there given, representing a scene on Cayuga Lake. The 

 rock at the place is the Moscow shale. 



Economical Products. 



The Hamilton beds afford the best flagging-stone of the country. 



The Black shale, or Genesee shale, is remarkable as an oil-yielding 

 rock. This is true in New York and all through the West, wherever 

 it has much thickness. In Tennessee, the shale sometimes yields fif- 

 teen to twenty per cent, of mineral oil and tars. In Ohio, where it 

 is 350 feet thick, it contains, according to Newberry, ten per cent, of 

 combustible matter, and is therefore equivalent to a coal seam 40 feet 

 thick. 



This oil, obtained from the rock, is not present in it as oil, for no 

 solvents will separate it : it is produced by the heat of distillation 

 out of the carbonaceous substances present. This shale has been 

 regarded as the main original source of the oils in the oil region of 

 Ohio and Western Pennsylvania ; but there is reason to believe that 

 part at least of the supply in these regions has come from the Cor- 

 niferous limestone below it. 



In the oil regions, gas is often given out from the borings, and is 

 used for lighting and warming houses, and various other economical 

 purposes. 



The same rock often contains much pyrite, and might be used for 

 making copperas and alum. Efflorescences of both of these substances 

 are common in sheltered places. It is a source also of numerous 

 sulphur springs. 



II. Life. 

 1. Plants. 



The carbonaceous material of the black Marcellus shale is of or- 

 ganic origin ; but whether due to sea-weeds or to land-plants, or partly 

 to fishes or other animals, has not been ascertained. 



In the Hamilton beds, the evidences of verdure over the land are 

 abundant. The remains show that there were trees, as well as smaller 

 plants ; that there were forests of moderate growth, and great jungles 

 over wide-spread marshes. 



These terrestrial plants include Lycopods, Ferns, and Equiseta, the 

 three orders of Acrogens, or higher Cryptogams, and also Gharce, but 

 no true Mosses ; and with these there were Gymnosperms, or the 

 lower Phenogams. 



1. Lycopods. — The Lycopods of the Hamilton were of three types ; 

 (1) the Psilophyta, or the slender forms, which were the earliest repre- 



