204 TERTIARY SYSTEM. 



Slate of the beds, they are liable to slide down in mass. This movement may extend for 

 some consideral)le distance, and sometimes the sand has flowed into and filled the exca- 

 vations. There are, also, occasional faults in the clay and sand beds ; and, as in other 

 cases of a like nature among rocks, these faults give origin to springs. 



In the excavations in the city of Albany, a boulder is sometimes found in the clay, but 

 ahv^avs near the top of the formation. This assertion is intended to be confined to the true 

 sedimentary beds : it does not apply to the drift beds, which are sometimes exposed in 

 this valley. They repose generally upon the rock, and belong to the base of the forma- 

 tion, or to that moderate drift period wliich followed tlie deposition of the clay and sand 

 beds whose strata are uniform and unbroken, and which are comparatively free from 

 coarse sand, gravel and boulders. 



The sand of this formation is yellowish, porous, and rather barren. There are beds, 

 however, which are rpiite the reverse of this, and are really remarkable ; they form the 

 excellent moulding sand so well known in the vicinity of Albany. It is a sand whicli is 

 evenly mixed with loam, and which retains a certain amount of moisture under all cir- 

 cumstances. Even when exposed in heaps in dry weather, it appears moist beneath the 

 surface, and when pressed in the hand, retains the shape and form given it. This sand, 

 too, forms an excellent soil, of which we shall have occasion to sjjeak hereafter. 



§ 3. Marl and peat. 



Before dismissing those formations which have been called tertiary and post -tertiary, it 

 is proper to speak of the deposits which are considered by all geologists as the most recent, 

 and which really are the proximate formations that connect the modern deposits with the 

 ancient; the present, with the past; and in whicli geological changes bear an aspect more 

 real than those of the Carboniferous or Silurian era. It is by means of the fossils of a period 

 just anterior to the present, and which is not to be regarded precisely as a tangent to it, 

 but rather as forming with it a continuous portion of a great circle, that we may familiarize 

 our minds with the nature of those peculiar changes and phenomena which clothe the 

 history of the earth with so much interest. Just before us, there lived races of animals, 

 whose forms and whose habits scarcely differed from those which are now familiar to us : 

 they were really members of different families at present existing and known to us, 

 having affinities and relationships with them of the closest kind. Knowing the living and 

 the present, we also know the dead and the past. Conjoined in both periods, we have 

 the last term of a series, from which we may travel back to the remoter periods, and trace 

 up the analogies as they have Ijeen successively developed. We judge the past by the 

 present; and from the store of knowledge accumulated by modern discovery anil modern 

 induction, we are enabled to supply many of the links which are wanting to complete 

 the system of a perfect scale of being, such as shall represent the whole of life and 

 organization as it was made for the earth. The chain is complete, and its extremities are 

 united in one eternally revolving circle of life. It looks an ocean of being, formed by the 



