250 Geology of the Catskalls. 
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, efflorescing 
from the mineral cavities of the rocks. 2d. In the sand- 
stone about two miles east of the Mountains, I discovered 
malachite (green carbonat of copper) with its usual associates, 
quartz and sulphat of barytes. 3d. The Fer Ologiste 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- 
ginal vegetable. The acidification of the sulphur (one of 
the ingredients of the Pyrites) accounts satisfactorily for the 
production of the sulphate of iron, as well as the sulphate of 
Alumine with which itis found in intimate connexion. 
References to the Engraved Plan. 
No. 1. Ledges of schistose sandstone running in a diree- 
tion about N. by E. and S. by W. containing numerous pe- 
trifactions—position nearly horizontal. 
No. 2. A fine argillaceous slate, embracing very “few, 
and these indistinct organic remains. Its inclination is 
much greater than that of the preceding class, and where I 
have observed them contiguous, the schistose sandstone has 
invariably occupied the highest position. The Argillite is 
evidently of earlier formation. 
No. 3. Sandstone similar to that denoted by No. 1. 
No. 4. Slate not differing essentially from that of the sec- 
end class. . 
No. 5. Ledges of Limestone nearly horizontal and par- 
allel with the strata already described. Insome instances 
there is a sudden and remarkable deviation from. this posi- 
tion, andthe strata become inclined at an angle of 20° or 30°. 
