460 
GEOLOGY OF THE FIRST DISTRICT. 
Limestone was observed in two places between Verplanck and Henry J. Cruger’s, by the 
upper road ; one was near the church. 
Plate 14, fig. 5, exhibits the rocks and their position as observed by Prof. Cassels, between 
Tarrytown and Whiteplains ; but there is one bed of limestone that undoubtedly crosses the 
line of that section in the valley of Sawmill river, that was not seen. The bed has been ex¬ 
amined both north and south of the line of section, and where the section was made, was 
probably covered by alluvial or quaternary depositions. 
As the rocks associated with the limestone have been traced along the shore from Peekskill 
to Sparta, except where the quaternary and alluvial depositions occupied it at Teller’s point, 
and a mile or two above, I will continue to trace them with the associated limestone beds that 
reach the Hudson successively. 
Hornblendic gneiss with veins, interlaminated beds, and irregular masses of granite, form 
the shore from Sparta to near Tarrytown. These rocks are finely exposed to view, and are 
worthy of a more rigid examination than I was enabled to make of them. Some of the gneiss 
rocks contain no hornblende, and some are very micaceous. The gneiss that contains no 
hornblende, is generally red like that at Mrs. Beekman’s quarry, about two miles north of 
Tarrytown, and the granite beds and veins are of the same color. 
From Tarrytown to below Dobbs’s ferry, the shore is mostly skirted by the quaternary 
formation ; but the rocks frequently emerge along the shore, and are mostly varieties of gneiss. 
About one and a half miles below Dobbs’s ferry, the white granular limestone emerged on the 
shore, and extended along it for a mile or more. The reddish color of the soil and of the 
rocks for some distance before the limestone was seen, had been observed, and was known to 
indicate the proximity of that rock. Some of this limestone will make good lime, and perhaps 
good marble ; but much of it is interstratified with layers of a siliceous limestone loaded with 
magnetic sulphuret of iron, like similar layers on the shore between Singsing dock and the 
State Prison. 
A limestone quarry is worked near the shore in this bed of limestone, about one and a half 
miles below Dobbs’s ferry, and a railway with a double track is laid to transport the stone from 
the quarry to the wharf. The rock is a beautiful white crystalline limestone, and if the quarry 
should be worked to a greater depth, would probably afford large and sound blocks of good 
marble. Gneissoid rocks which are frequently hornblendic, succeed the limestone on the 
east, and emerge successively on the shore between this limestone bed and Yonkers. The 
rocks are not seen continuously on the shore, but they emerge occasionally through the qua¬ 
ternary. 
The rocks continue about the same to the mouth of Spuytenduyvel creek, at the north end 
of New-York island, where the limestone of Kingsbridge, which has already been described, 
succeeds, and occupies the shore of the creek for a half mile or more; while gneiss, with 
granite in beds and veins, forms the rocky ridge on the west, along the western shore of the 
island from Tubby hook southwards. 
There are a few beds more of the Metamorphic limestones somewhat different in character, 
that remain to be described in this class, viz. that of the Anthophyllite locality in the city of 
