82 
[Assembly 
verse, in increasing the area of estates, in covering them with 
fresh water, by darning up the outlets of small streams, &c., that 
I have deemed it necessary to bring forward some of the most im- 
portant of the facts bearing upon such objects. Details of local 
geology will generally be brought forward in the final report only. 
Land Slides. 
Land slides on a small scale, are of very common occurrence on 
many parts of the north coast of Long-Island. They are in some 
places caused by the sea undermining the cliffs, so that the super- 
incumbent masses crack off at a short distance from their edges, 
and slide down to a lower level, carrying with them trees and 
shrubs, and sometimes even without changing their relative posi- 
tion. These phenomena are common along the north shore, but 
they are more striking and numerous where there are clay-beds, 
and particularly so, where the clay slightly inclines towards the 
sea. Where the cliffs are high, they present an appearance of 
steps, in consequence of the successive slides.* 
Another cause of slides is, the undermining action of land- 
springs, which often convert sand into quicksand, so that it flows 
from the cliffs, and bears along with it the superincumbent masses; 
but in most instances they are caused by springs, rendering the upper 
surface of clay beds slippery, so that large masses from the cliffs slide 
down upon the shore, and even into the sea. Several acres have 
thus slidden otf at once, and sunk in level from 20 to 150 feet. By 
this means ravines of considerable extent are frequently formed 
* Small slides have been observed about Albany, caused by springs rendering the clay 
slippery next the rock, which is frequently smooth, and allows large masses to slide into 
the ravines and valleys below. 
The slides at Troy during the summer of 1S36, and on the 1st of January, 1837, were 
also caused by springs of water. The locaUty at which these slides took place, presented 
a nearly vertical face of gravel and clay beds, of 227 feet in height. The upper part of the 
cliff probably cracked, and the land spring (which forms a considerable stream of water, 
and which from some unknown cause had been stopped,) filled the fissure, rendered the 
clay slippery, and acting by its great hydrostatic pressure, burst off the cliff, which tum- 
bled in huge fragments, sliding along as a mass of ruins, carrying every thing before it. 
The avalanche, after reaching the level ground, slid onwards about 800 feet, crossed one 
street and stopped at the second, crushing three houses and two barns, and destroying 
the lives of several persons, who were buried beneath the materials. The avalanche was 
accompanied by torrents of water and mud, rushing with a roaring noise over the fallen 
ruins. The fragments of the cliff form a very uneven surface of small iri-egular hills; the 
masses of clay are in huge fragments, with their layers placed at every angle of inclina- 
tion and in every direction, and cover a surface about equivalent to 200 yards in length 
by 100 in breadth, and from 10 to 40 feet deep. By a moderate estimate, 200,000 tons 
of earth were thus transported to a distance of about 200 yards. 
