No. 275. 1 
261 
should lime admit, will be given as an appendix to the report. For 
the present we add the note which was made in passing up to the top 
of the hill. The first product met with is the gravel of the second al- 
luvial. This is followed by the red earth, and which always forms the 
third or upper alluvial. Beyond these, in rising, is the drab coloured 
slaty rock, the first seen. The next resembles the usual envelope of 
the lower plaster. To this about 20 feet of layers, with small pores, 
succeeds, and then an interval from depth of soil for some distance takes 
place, and then again the rock masses which compose the upper part of 
the hill. The first is a marly shale. Then mixtures with more carbo- 
nate of lime, some compact, some crystalline, confused, aggregated, 
and presenting cavities lined with crystals of that mineral, and contain- 
ing also sulphate of strontian in the mass and in the cavities. With 
these and above these, are other aggregates like serpentine, marble, &c. 
with purplish shale, or slate which are followed by a green and black- 
ish trap-like rock, as to appearance, but too soft for that rock. After 
this, that is above it, is the mass which resembles the material which 
forms the arch of the lower beds of plaster, and this is covered by the 
upper porous or " vermicular rock." 
Magnesian Deposit. 
This deposit terminates the group. It appears to be a thick series of 
what is probably a magnesian limestone. Usual colour is of a brown- 
ish drab; and also dove, breaking with rather an earthy fracture. Its 
great characteristic, and which will suflfice for the present report, is its 
fibrous cavities, caused by the crystallization of sulphate of magnesia, 
as we fully proved in the last report. These cavities are very nume- 
rous in the series, and in every locality where they are found show that 
they follow the gypseous masses. The most numerous are found at 
Hungerford's plaster quarry, and also by the rail-road just below^ Split 
rock quarry, near Syracuse. Likewise near the upper plaster quarries, 
on Cayuga lake, the mill at Troopsville, &c. &c. 
The cavities in this series are more frequently found in a vertical po- 
sition, like veins, than in an horizontal one, as is usually the case. 
The cause seems to be, the existence of imperceptible cracks, by which 
water has had access to the rock, and the salt has crystallized in accor- 
dance with the direction taken by this fluid. This opinion is confirmed 
by the facility which the rock breaks with more or less even surface in 
the vertical direction, and by toughness and unevenness in the horizon- 
tal one. The cavities strongly contrast with the rock, from thin lining 
of coa)y matter. 
