DRIFT DIVISION. 
209 
Lieut. Col. Imrie observed scratches and surfaces smoothed by attrition, on the trap rocks on 
the Campsey hills, and in the glens and valleys, and on an elevated plain. Boulders of trap, 
covered with scratches, were also observed, with their angles turned to the northwest, and 
showing, by this means and the scratches, the direction of the current.* 
Prof. L. D. Gale, speaking of grooves, furrows and scratches of the Island of New-York, 
says: 
“ Diluvial grooves and scratches have been found in every section of the island, from Six¬ 
teenth-street on the south, to 200th-street on the north, (or to the southern termination of the 
limestone;) and from the banks of the Hudson on the west, to Harlem river on the east. 
The furrows generally are most distinct where the .rock has been recently uncovered, and 
least so where it has long been exposed to the action of the elements. They have been found 
on the highest rocks, and at the lowest tide-water marks, being a difference of more than 
one hundred feet perpendicular height. The furrows are always most strongly marked on the 
northwestern slopes of the hills, and least so on the southeastern. In many instances they 
are very distinct on the western and northwestern slopes, extending to the highest point of the 
rock ; but no traces are to be seen on the eastern and southeastern slopes, although both slopes 
are equally exposed. 
“ Direction of the furrows. Observations of the diluvial furrows were made in between 
sixty and seventy different places on the island. Taking together the whole series of obser¬ 
vations, the general course of the current was from northwest to southeast, or north forty-five 
degrees west, but varied in the extremes from north twenty-five degrees west to north forty- 
eight degrees west, making a difference of twenty-three degrees. Of the whole series of 
observations, thirty-nine were north forty-five degrees west, twelve varied from north forty-five 
degrees west (seven being north thirty-five degrees west), two were north forty-eight degrees 
west, and a few scattering ones varying from north thirty-five degrees west to north forty- 
five degrees west. 
“Abundance of the furrows. The furrows occur most abundantly in the middle portions of 
the island, between the city and the Harlem and Manhattanville valley, somewhat less in the 
western, and least of all in the eastern. 
“ Direction of the furrows in particular neighborhoods. Half of all the places where the 
furrows were noticed were in the middle portion of the island, in the line of the Eighth 
avenue from Sixtieth-street to 105th-street, where without exception the direction is north 
forty-five degrees west. About one fourth of all are on the west side, and vary but little 
from north thirty-five degrees west; and about one-eighth on the eastern side, where the 
direction varies from north twenty-five degrees west to north thirty-five degrees west. In 
connection with this subject, I have examined the surface of the greenstone on the neighboring 
shores of New-Jersey, and find their grooves and scratches abundant, and their general direc- 
* Transactions of the Wernerian Society, p. 35; and Buckland, Rel. Diluvian®, p. 202. 
Geol. 1st Dist. 27 
