LONG ISLAND FROM MARINE CAUSES. 381 



detached from solid strata, and to have been rolled and 

 worn since. They consist mostly of granite and gneiss. 

 There are some huge masses of actinolite or radiated as- 

 bestos, and many of ponderous black shoerl among them. 

 Stones of many kinds, consisting of quartz, shist, ferrugi- 

 nous oxyd, breccias, and pebbles formed of the granite 

 and gneiss, abound every where among the rocks. 



. 



These loose and rolled rocks are most abundant in the 

 towns of North-Hempstead and Flushing, particularly 

 the former. Their great weight and bulk must have re- 

 quired extraordinary power to detach them from their 

 primitive beds, and to have placed them \vhere they now 

 lie. Along the shores and over the fields, stones have 

 been found now and then, in which prganic remains of 

 shells could be distinguished. 



There is a ridge of hills upon Long-Island, separating 

 it into two sections, the north and the south side. They 

 extend from New-Utretcht in the west, to the neighbour- 

 hood of Southold in the east. They are highest in North- 

 Hempstead, and gradually slope away on both directions 

 until they disappear in King's county, near the Narrows, 

 and in Suffolk, as they approach River-Head. 



Their greatest elevation at the Harbour Hill, as found 

 by Capt. Partridge, accompanied by Mr. Haines, Mr. 

 Griffith, Professor EJUcott, Judge Mitchill, and myself, in 

 the summer of 1816, is three hundred and nineteen feet. 

 My letter to Mr. Dallas, then Secretary of the Treasury 

 of the United States, (of October 16, 1816) contains the 

 particulars of that expedition and experiment. 



The north side of the Long-Island ridge of hills is so 

 Different from the south side, that a traveller naturally 



