106 J. D. Dana—Results of the Earth's Contraction. 
dolerite of East Rock, New Haven, Conn., gave Professor G. J. 
Brush for the specific gravity 3-09—8-085; from West Rock, ib., 
Si Al e Mg Ca K,Na ign. 
1. West Rock, 52°37 1231 1313 603 104 262 0°94= 9814 
2. Palisades, 53°9 ‘ 80 103 80 = [23] 00 
There are variations in the dolerite of the regions above 
referred to, depending on the proportion of the feldspar, and 
also on the presence of water. But they occur in various 
parts of the several regions, instead of characterizing any one 
(and 12 miles from the southern margin of the map); and the range which 
extends from these hills north continues to Mt. Tom, near Northam in Mas- 
usetts. The range to the east, south of this bend, continues southward to 
the 
urassic sandstone areas. There is also a series in the North Carolina 
ae 
