PRIMITIVE ROCK AT THE CITY OF NEW-YORK. 387 



has been overspread by the more recent alluvion now 

 under consideration. 



The alterations perpetually making by public authori- 

 ty, afford lessons to the naturalist, as instructive as if they 

 had been made for his special use. While streets are 

 opening, and hills digging down, there are the fairest 

 opportunities of examining how the strata lay and of what 

 they were composed. 



These alluvial materials are disposed horizontally, 

 waving in some places,and dipping a little; but convincing 

 the beholder that they were so arranged by the action of 

 water. 



The constitution of these strata, upon which the city of 

 NeW-York actually stands, is sand, gravel, rounded stones 

 fit for paving, and loose rocks, some of them of enormous 

 magnitude. There is a scarcity of clay in the soil ; that 

 is to say, it is not stiff enough to form bricks. At most it 

 is but a sandy loam. 



Nodules of stony matter, disclosing by their fracture 

 petrified shells and their impressions, have been often 

 found. During this season of 1817, such organic relicks 

 were brought to me from Corlear's Hook, the Battery, and 

 a place situated between the Bowery and Broadway. 



Broken pieces of compact shistus, alone, and associated 

 quartz, have frequently been found. 



The rounded rocks are sometimes six feet in diame- 

 ter. In the progress of alterations made by public 

 authority, they are daily disappearing from view. 

 .Part of them are buried in the ground ; but the 



