Geological Survey of the Great Canal. 373 
gard every new step of this kind, as an vaddition to our na- 
tional resources. 
Excepting the natural alum of the caverns in Tennessee 
and of some other regions of the West and South, and that, 
occasionally found, in our schistose rocks, and needs in these 
cases, more or less, for domestic dyeing, and other purposes, 
we were not aware that the United States possessed any re- 
source for this article independent of the foreign markets. 
since, we were informed that a manufactor 
was established at Salem in Massachusetts, and the proprie- 
tors have recently put us in possession of a set of specimens, 
which prove that the effort has been completely successful. 
mong the crystals of alum, are some of great size, and ex- 
quisite beauty and transparency, exhibiting to the naked eye, 
in a very striking manner, the successive ]ayers of super-posi- 
rt 
edges and angles, which are in every part, fees by trun- 
cations. Some crystals of rather smaller size are quite or 
nearly perfect. We are aware that fine crystals of alum are 
not rare in manufactories, but we have not seen these equal- 
led even by the similar productions of the celebrated establish- 
ment near Glasgow. There can be no question from the 
appearance of these crystals, as well as from that of the 
amorphous masses, of the extreme purity of these materials. 
Perhaps they are even purer for this reason, that the alum is 
not manufactured (as we understand,) from the usual source, 
namely, the decomposed alum slates, but from the direc a 
thetical union of sulphuric acid with the argillaceous eart 
The sulphate of copper, (blue vitriol,) made at this estab- 
lishment, is equally seheet in its kind, presenting crystals of 
extreme finish and beau 
e skill manifested in the manufacture of these articles, 
clealy evinces, that the persons conducting this establish- 
ment, are quite equal to the task which they have underta- 
ken, and are fairly entitled to the public confidence.—Ed. 
10. Geological Survey on the Great Canal. 
“The of alibat of Albany, the Hon. Stephen Van Rensse- 
laer, with his usual liberality, has undertaken the expense of 
