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 Devonian period, the third in succession of these great epochs.  I need hardly remind those of my readers 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 sand—­or lime-stone, 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.  Now, what does this fossil creation tell us?  It says this:  that, in the Silurian period, the first in which organic life is found at all, there were the three classes of Radiates, the three classes of Mollusks, two of the classes of Articulates, and one class of Vertebrates.  In other words, at the dawn of life on earth, the plan of the animal creation with its four fundamental ideas was laid out,—­Radiates, Mollusks, Articulates, and Vertebrates were present at that first representation of life upon our globe.  If, then, all the primary types appeared simultaneously, one cannot have grown out of another,—­they could not be at once contemporaries and descendants of each other.

The diagram on the opposite page represents the geological periods in their regular succession, and the approximate time at which all the types and all the classes of the Animal Kingdom were introduced; for there is still some doubt as to the exact period of the introduction of several of the classes, though all geologists are agreed respecting them, within certain limits, not very remote from each other, according to geological estimates of time.

RADIATES. 
Polyps.  Acalephs.  Echinoderms. 
T | Present,.........|.........|...........|...... 
E | | | |
R | Pliocene,........|.........|...........|...... 
T | | | |
I | Miocene,.........|.........|...........|...... 
A | | | |
R | Eocene,..........|.........|...........|...... 
Y | | | |
| | |
S | Cretaceous,......|.........|...........|...... 
E | | | |
C | Jurassic,........|.........|...........|...... 
O | | | |