Limestone Belts of Westchester County, N. Y. 365 
lead to the Sound on one side and to the valley of the Har- 
lem railroad on the other. Along this railroad, limestone 
again appears, and before reaching it there is a return to mica- 
ceous gneiss and mica schist. 
Areas 7 and 8.—Of these areas at Yonkers, number 7, or the 
western, follows the course of a north and south bend in Saw 
i iver, and has a width of at least 100 feet. It lies 
beneath the city of Yonkers, and I am indebted for the facts 
respecting it to Mr. W. W. Wilson, Engineer of the Yonkers 
Water Works. Indications of a more eastern belt (No. 8) 
occur along the Saw Mill River valley, just north of the city, 
in the existence of loose masses of limestone on the east side 
of the river. But I found no outcrops in my observations 
along that southern portion of the valley, and its width an 
length are therefore undetermined. It is possible that the two 
areas may be one cut into two by a fracture and a horizontal 
or oblique faulting. The rocks are not open to view for a 
decision of this point. 
rea 9.—This small area, on Grassy Sprain Brook, has a 
width to the south of 500 yards. The strike is N. 10°-20° E. 
Areas 10, 11 and 12.—Kast of the last, on the River Bronx, 
a limestone belt begins near Bronxville, which, in Tuckahoe 
and Scarsdale, is the site of many marble quarries. The strike 
is N. 22°-27° E. This limestone belt tapers out to the south, 
while to the north, and for the most of its course, it is divided 
into two parts separated by a band of mica schist and gneiss. 
It is probable that the whole corresponds to a decapitated anti- 
clinal having its inclined axis dipping at a small angle to the 
south. To the north of the Scarsdale depot the eastern line is 
not traceable, and the western line appears to thin out. 
imestone re-appears on the Bronx 100 to 200 rods to the 
north of the last, just east of the railroad—that of area 11 
—and thence continues to Hartsville, where the strike is N. 
17°-24° EK. A narrow strip of low land follows the east side of 
the Bronx nearly to White Plains, and it is possible that the 
belt is continued beneath it. About a mile and a half north of 
hite Plains a small area of limestone shows itself, No. 12, 
the most of the exposure of which is due to the removal of the 
Stratified drift. 
Area 13,—Again, along the Hudson, north of Yonkers, 
occurs the Hastings belt. It was formerly visible at Dobb’s 
Ferry ; and it was cut into, as I learn from Mr. Benjamin S. 
Church, when excavations were going on there for the Croton 
aqueduct. This river-border belt may have much greater 
length than is given it on the map, and greater width also; for 
the high terrace deposits (stratified drift) of the valley conceal 
all shore rocks. The adjoining schists are gneiss with nearly 
vertical dip. 
