70 Geology of Massachusetts. 
These facts ought to be kept in mind in forming an estimate of our 
mineral resources. Yet imperfect as is our acquaintance with these, 
J think we need not fear a comparison, in this respect, with any other 
part of the country. Other States possess particular minerals which 
are more valuable and interesting, and calculated to awaken public 
attention more than ours; yet where is the territory abounding in a 
greater number of rocks and minerals, of real and permanent utility, 
whose quality is excellent and whose quantity is inexhaustible? They 
are, indeed, of such a character, that they will increase in value for 
several generations to come. That is, we may calculate that the de- 
mand for them will increase during that period, and this demand will 
lead to the discovery of varieties really more valuable. 
Thus far we have regarded our geology only in an economical 
point of view. I hope to show in the subsequent parts of my Report, 
that it is not less interesting to the man of taste and science. 
Respectfully submitted, 
Epwarp Hircucocx. 
Amherst College, Jan. Ist, 1832. 
P. S.—Since the above account was in type, I learn, that in Le- 
ominster, in Worcester county, there isa rich alum rock. It ap- 
pears to be a decomposed mica slate, and contains abundance of 
beautiful plumose, or feather-form alum, like that of Milo, one of - 
the Grecian isles, mixed with the green crystals of copperas, or sul- 
phate of iron. There can be little doubt, that it proceeds from the 
decomposition of iron pyrites in the rock 3-the acid, formed from the 
sulphur, then unites with both the iron and the alumina,- and thus 
forms the two salts. If these salts, and especially the alum, or the 
materials, which by proper treatment, may easily produce it, should 
prove to be abundant, the discovery may become practically impor- 
tant. I have not seen the specimens, but derive my information from 
Prof. Silliman, who has examined them; and who remarks, that it is 
common in this country, to find alum, formed in mica slate 3 a fact 
which appears to have been scarcely observed in Europe, where a 
variety of clay slate, or shale is the common alum rock. 
e Rev. Mr. Boutelle, of Leominster, can give more particular 
information as to the local facts. 
