198 
[Assembly 
current was more than 100 feet in depth. 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 west- 
ern and northwestern slopes, extending to the highest point of the rock, 
but no traces are to be seen on the eastern and southeastern slopes, al- 
though 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 observations, the general course of 
the current was from northwest to southeast, or north 45° west, but va- 
ried in the extremes from north 25° west to north 48° west, making a 
difference of 23°. 
Of the whole series of observations, thirty-nine were north 45° west, 
twelve varied from north 25° west, (seven being north 35° west,) two 
were north 48° west, and a few scattering ones, varying from north 35° 
west to north 45° west. 
Mundance 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 neighhoi'hoods. Half of all the 
places where the furrows were noticed were in the middle portion of the 
island in the line of the 8th avenue from 60th-street to 105th-street, 
where without exception the direction is north 45° west. About one- 
fourth of all are on the west side, and vary but little from north 35° 
west, and about one-eighth on the eastern side, where the direction va- 
ries from north 25° west to north 35° west. In connection with this 
subject, I have examined the surface of the greenstone on the neighbor- 
ing shores of New- Jersey, and find their grooves and scratches abun- 
dant, and their general direction is north 45° west. Hence it appears, 
that the diluvial current which once swept over this island from north- 
west to southeast, on reaching the western shore was deflected south-, 
ward, as by the action of some force at a right or some other angle to 
its course; and that the same current, before it reached the middle of 
the island, again assumed a southeasterly direction, but was again di- 
verted southerly on approaching the eastern shore. That some portion 
of the current w^as diverted southerly on reaching the western shore of 
the island, is evident, not only from the diluvial furrows, but from the 
boulders of anthophylite found in large numbers in the lower part of 
