634 
GEOLOGY OF THE FIRST DISTRICT. 
APPENDIX. 
ADDENDA TO THE ALLUVIAL DIVISION. 
Land Slide. 
A destructive land slide at Troy, Rensselaer county, was described on pp. 33, 35, of this 
volume, as having occurred January 1st, 1837. A slide at the same locality, and still more 
destructive of life and property, occurred on the afternoon of February 17th, 1843. Ten 
dwellings were crushed and buried beneath the moving avalanche, and from thirty to forty 
persons are supposed to have been destroyed. The cause of the slide seems to have been 
the same as those of 1836 and 1837, at the same place, viz; 1st. Undermining of the hill, 
to get earth for filling in the streets and grounds in the lower part of the city ; 2d. The action 
of water accumulated in the sand and gravel beds above the clay, and in the fissures of 
partial breaks through the clay beds, rendering them slippery, and acting partially by 
hydrostatic pressure ; 3d. The yielding nature of the gravel beds underlying the clay beds, 
and which had been partially removed, leaving the superincumbent masses but slightly sup¬ 
ported. The main masses of materials of this hill are as follows: 
1. Sand and gravel beds extending from the top of the hill to a depth of thirty or forty feet. 
2. Greyish clay, containing clay stones of various forms, composed of clay indurated by 
carbonate of lime. 
3. Blue clay, very fine and saponaceous. 
4. Gravel and pebble beds down to the lowest level excavated : sixty to seventy feet. 
The following, from the “ Troy Budget,” of February 18th, 1843, and from the “ Troy 
Whig,” of the same date, gives some of the particulars of the event: 
“ The distance from the commencement of the slide to the outer edge of the deposit of 
earth which it has left, is not far from two hundred yards, the earth having slidden more than 
five hundred feet over a dead level after it reached the bottom of the hill. The soil being a 
remarkably unctuous blue clay, is doubtless the cause of the extraordinary space which the 
slide covered. The slide commenced about one hundred yards east of Fifth-street, and its 
southern extremity first encountered two houses adjoining each other on the east side of the 
street, both of which it destroyed. 
