Limestone Belts of Westchester County, New York. 25 
continuation of the formation (which extends for about two 
miles from Tompkins’ Cove to Stony Point village, where the 
Mesozoic Red sandstone appears in force), the slate changes in 
places to a massive quartzyte, often containing much blackish 
slate material, and looking as if it had been made out of a mix- 
ture of mud and quartz sand, with at times some feldspar. Re- 
membering that the making of beds of sand by moving waters 
involves the making of mud not far away, such transitions are 
no occasion for surprise ; and in view of the fact that the High- 
land Archean is close at hand—not three miles distant—the 
from the unchanged "bed. The looseness of texture shows 
that something has been removed, and this is probably, in part 
at least, calcareous material; and if so the bed should be 
classed with the limestone beds. This locality is by the west 
side of the eastern of two bridges, near the Spuyten Duyvil 
Iron Foundry, and stratigraphically but a short distance from 
the belt of limestone of the northern end of New York Island. 
intervening in the latitude of Singsing. No true unconforma- 
bility between the limestone and other strata has been ob- 
