250 Geology of the Catskills. 
evaporated, and deposits the alum in the form of a powder. 
It is here collected in considerable quantities, and employed 
without farther preparation as a substitute for the imported 
alum. I observed sulphur in the fissures of the same rocks ; 
to this no doubt the sulphate of alumine owes its origin. The 
same substance occurs in many other places, ap Ce 
from the mineral cavities of the rocks. 2d. In the sand- 
stone about two miles east of the Mountains, I ‘acon 
malachite (green carbonat of copper) with its usual associates, 
quartz and sulphat of barytes. 3d. The Fer Ologuste or 
specular iron frequently occurred in small quantities in de- 
tached masses of quartz. 4th. In the channel of a stream, 
two miles south-east of the Durhan meeting-house, (Greene 
county,) I found the sulphat of iron distinctly characterized. 
- The same rock in which this occurs, (a coarse variety of 
slate,) abounds with imperfect vegetable impressions, some 
of which are converted into coal, and the cavities which the 
decay of others has left, are occupied by sulphat of iron, 
which frequently presents the fibres and branches of the ori- 
eer vegetable. The acidification of the sulphur (one of 
he ingredients of the Pyrites) accounts satisfactorily for the 
oredaekion of the sulphate of iron, as well as the sulphate of 
Alumine with which itis found i in intimate connexion. 
References to the Engraved Plan. 
No. I, Ledges 0 of schistose sandstone running a direc- 
tion about N. by E. and S. by W. containing numerous pe- 
trifactions—position nearly horiz ontal.. 
No. 2. A fine argillaceous slate, cmbicacthg:) very few 
and these indistinct organic remains. Its inclination is 
much greater than that of the preceding class, and where 
have Ysa them contiguous, the schistose susan has 
invariably occupied the highest position. The Argillite is 
evidently of cariien  formati aA ay 
No. 3. Sandstone vishidn to that denoted by No. 1.. 
re Slate not differing essentially from that of the sec- 
No. 5. Ledges of Limestone nearly Reena and par- 
allel with shevahtina sabes ready described. In some instances 
there is a sudden and remarkable deviation fon this posi- 
tion, andthe strata become inclined at an angle of 20° or 30°. 
