We may add in conclusion a few remarks on the causes which 

 have brought the rocky strata of New- York from the original 

 level and unbroken condition in which they were formed, to the 

 waving and broken surface of hills and valleys which we now 

 see. It is probable, as we have before stated, that during the 

 slow process of their emergence above their native sea, the action 

 of waves and currents wore them deeply and extensively ; and 

 since they were fairly uplifted to their present elevation, the 

 elements have been unremittingly acting upon them until now. 



We know that, in all probability, no rocks newer than the 

 Carboniferous were ever deposited within the area of our State. 

 It seems therefore, that this region has been above water since 

 the Carboniferous period ; during all the countless ages while 

 the Permian, Triassic, Jurassic, Cretaceous and Tertiary forma- 

 tions were formed ; during the deposition of which the animated 

 population of earth has been changed many times. All of these 

 must have been made of sediments worn from pre-existing dry land. 

 We should expect, therefore, that this ancient land would show 

 the marks of vast erosion or wear. Such marks are found in 

 the long and deep river-valleys which cross the State, all of 

 which have evidently been worn out of the solid strata, the re- 

 maining portions of which form their bounding hills. They are 

 still being worn deeper and wider by rains and streams ; but 

 how far the action of these, continued through an indefinite 

 though vast period of past time, may be deemed adequate to 

 produce such enormous excavations, may be questioned. And 

 there are some valleys which have been excavated much below 

 the level of their outlets, so that they retain the waters and form 

 the remarkable series of lakes of which we have before spoken. 

 Such instances seem to require a different explanation, which it 

 is not easy to give. 



However inexplicable it may be, with our present knowledge, 

 the fact is plain that not only these valleys have been worn out, 

 but hundreds of feet of rocky strata have been removed from the 



