GRADATION AMONG ANIMALS. 93 



the investigation of this succession, because, in 

 consequence of its mode of formation, we have, 

 in the State of New York, a direct, unbroken se- 

 quence of all the earliest geological deposits. 



The ridge of low hills, called the Laurentian 

 Hills, along the line of division between Canada 

 and the States was the first American land lifted 

 above the ocean. That land belongs to the Azoic 

 period, and contains no trace of life. Along the 

 base of that range of hills lie the deposits of the 

 next great geological period, the Silurian ; and 

 the State of New York, geologically speaking, 

 belongs almost entirely to this Silurian period, 

 with its lowest Taconic division, and the Devon- 

 ian period, the third in succession of these great 

 epochs. I need hardly remind those of my read- 

 ers who have travelled through New York, and 

 have visited Niagara or Trenton, or, indeed, any 

 of the localities where the broken edges of the 

 strata expose the buried life within them, how 

 numerous this early population of the earth must 

 have been. No one who has held in his hand one 

 of the crowded slabs of sandstone or limestone, 

 or slate full of Crustacea, Shells, and Corals, 

 from any of the old Silurian or Devonian beaches 

 which follow each other from north to south 

 across the State of New York, can suppose that 

 the manifestation of life was less multitudinous 

 then than now. 



