20 Geology and Mineralogy of apart of Massachusetts, &c. 
The argillite along the east side of the Taconick range, 
has sometimes a little talc mixed with it, forming talco-ar- 
gillaceous slate. 
Beds of argillite, resting on limestone, are found low 
down in the valley of Williamstown. : 
The primitive argillite is not disintegrated so rapidly as 
the transition. The soil of the argillaceous district is more 
fertile and productive than of any other portion of the section, 
except the alluvial. This fact has been remarked by ag- 
riculturalists, and corresponds with the statement of some 
English geolozists. The same fact is noticed in the Geology 
of Rensselaer County, page 23. 
On the use of roof slate upon buildings, it may be prop- 
er to mention a fact stated by a very respectable gentleman 
of Troy,—that the smaller pieces of slate were found to 
make a more durable roofing than the larger, the former be- 
ing much less liable to crack and loosen by the action of 
heat and cold than the latter. 
The argillite seems to pass into chlorite slate occasional- 
ly,or, at least, chlorite slate is associated with it, and taleco-mi- 
caceous slate, in several places. Chlorite slate occurs in 
Pownal, Peiersburg, &c. Onthe east side of the Taconick 
range, it often contains magnetic oxide of iron, in octoedral 
crystals. In Petersburg it forms considerable hills, and is 
found in considerable quantities in the towns south of this 
place. 
In the south of Bennington, Vt. is a small hill of argillite, 
which approaches the variety, called graphic slate. Its co- 
lour is dirty black, fracture rather earthy, and streak often 
black. It contains crystals of sulphuret of iron, which are 
often changing to the hepatic sulphuret. The soil arising 
from the disintegration of the slate, is nearly black. The 
whole hill has the appearance, which might result from a 
recent combustion. Several years since a shaft was sunk 
here for the purpose of finding coal. It was not indeed 
continued through the rock. The geologist is aware that 
coal is not to be expected at this place, such is the geologi- 
cal position of the rock. The principal road from Ben- 
nington to Pownal passes over the side of this hill of argil- 
lite. The slate here is also tortuous, noticed by Prof. Sil- 
liman, Vol. IV. p. 43. 
