Look at the rocks themselves. What are they? Some are 

 soft and decompose rapidly; others are harder and withstand the 

 elements for a longer period. But all in course of time will dis- 

 integrate and form clay or sand, accordingly as they were shaly 

 or sandy rocks. Such rocks are in fact nothing but hardened 

 clayey or sandy mud. The shells in them prove that the sands 

 and mud before hardening formed a part of an old sea-bottom 

 where sea-shells lived, died, and were buried beneath more sand 

 and mud washed over them by inflowing rivers. If the water is 

 deep, or the bottom of the sea is gradually sinking, the thickness 

 of such deposits may become very great — several thousands of 

 feet. The lower beds become intensely compressed and hardened 

 after the lapse of long ages, especially if they are subjected to 

 volcanic heat and activity. If then a movement of the earth's 

 crust takes place and these low T -lying beds are raised above sea 

 level they are visible to man in quarries and other places as here- 

 tofore stated, and he terms them "hard rocks"; the shells and 

 other traces of life they contain are called fossils. 



That the conditions under which the rocks in southern New 

 York were deposited or formed may be clear to the mind of the 

 reader the following two outline maps have been inserted (Fig's. 

 3 and 4). They both show the same area (see degrees of Lat. 



jfr 



77* 



*v 



^L 



44* 



AW<r - The mtttor geqgrafhiml feet* 

 tt*ts cf tht$ land area during Upper 

 Dewnftin titnet are unknown JJfe 

 ddiraiutacks and other mountains to 

 the Rmth and the Taconta range to the 

 east were doubtless then more prominent 

 than they are today 



<tf 



F *g- 3- 



and Long.), the one approximately as the area appeared in De- 

 vonian times, the other as it appears to-day— showing especially 



