Geology of Massachusetis. 13 
ral, produces a favorable opinion as to the influence of this rock upon 
the soil, though very much must be imputed to good management. 
This formation in the Connecticut valley furnishes but little arable 
land, and that of rather a sterile character. 
Porphyry and Compact Feldspar. 
‘These rocks differ but little in an agricultural point of view. They 
are of quite limited extent and are decidedly the hardest and most un- 
yielding of all our rocks. ‘They occupy the greater part of the sur- 
face, and the scanty soil that has formed a lodgment in their ine- 
qualities, is not of the first rate character. 
Sientte and Granite.. 
Sienite is intermediate in its characters between greenstone and 
granite, although most commonly it is only a variety of granite. Both 
rocks are little liable to decomposition, and occupy a large porportion 
of the surface with their naked and rugged projections. Still, the soil 
found among them, particularly on the granite, is generally of a superior 
character, probably from the fact that most of it must have been de- 
rived from decomposed vegetable and animal matter. Hence it is 
usually of a dark color and fine texture, and not coarse and sandy 
like the soil above the granites of Europe, that more easily suffer 
decomposition. 
Should the preceding cursory remarks be the means of exciting 
the attention of intelligent agriculturists, to the connexion between 
rocks and soils, an important object willbe attamed. I have said 
enough to show that almost all known varieties of soil exist in Mas- 
sachusetts. But much improvement remains to be made in our 
agricultural concerns, before the excellencies of our soil are fully 
developed. It is but a moderate estimate to say, that the general 
adoption of an enlightened system of cultivation, would, in a few years, 
double the produce and the value of our improvable lands. ‘That is 
to say, such would be the speedy result, if all our farmers were to 
manage their lands as a few now do. 
USEFUL ROCKS AND MINERALS IN THE STATE. 
I shall next proceed to give an account of those rocks and min- 
eral subtances found in the State, which have been, or may be 
useful in the arts, and are consequently objects of pecuniary impor- 
