386 INLAND ALLUVION SUPERINDUCED OVER 



ty to be laid in courses, for the construction of walls* 

 The battery near the southwest castle is underlaid by 

 such stratified rock ; though now almost entirely covered 

 up by art in the progress of improvement. In thousands 

 of spots over the island, their naked backs rise above the 

 Surface. Great labour and expense have been necessary 

 for opening the streets and avenues through them. At 

 Hellegate and Bloomingdaie these rocks appear in their 

 proper and geognostic forms; making a spectacle highly 

 worthy the notice of all persons of taste as well as of 

 science. 



Upon this foundation of ancient stratified rock, a very 

 different and modern deposite has been made. This 

 is more considerable towards the middle and southwest, 

 south, and southeast side, th'an at the other extremity near 

 Kingsbridge and Haerlera. In its passage by the island, 

 the Hudson's direction is considerably to the westward 

 of south. 



The inundation from the lake beyond the mountains 

 has left some strong marks of its action. 



To the eye of the geologist, it looks as if a portion of 

 the overwhelming torrent, repelled by the Trap-wall at 

 Fort Lee, changed its direction, and opened the channel 

 of Haerlem river, filling its former estuary with the allu^ 

 vial matter that at this day constitutes Haerlem flats. 



Like Long Island, Staten Island, and the Neversink re- 

 gion near Sandy Hook,.there is evidence, a little south of 

 Bellevue, of an oceanic stratum of sand with the broken 

 shells of clams and oysters scattered throughout it. This 

 marine stratum, as well as the granite on which it 



