38 GEOLOGT. 



greater part now used both for schools and roofs, is 

 r ought from Wales. 



This rock is composed principally of clay, and hence 

 soils, where it abounds, are of the same character. If 

 argillite is put in a road where it will be finely pulve- 

 rized by wheels, it forms a mass differing but little from 

 a bed of clay. 



This rock is neither the most ancient, nor the most 

 recent. It was evidently formed after the primitive 

 limestone, but previously to the secondary deposits of 

 the same rock. 



Lime has already been mentioned, both as an ancient 

 and a modern rock. A few ancient deposits are found 

 in New England. Numerous and almost boundless 

 deposits of modern or secondary limestone, are found in 

 New York, and States still more west and south. The 

 masses found in New England are generally of a coarse 

 crystalline structure, those at the west and south, more 

 compact, and they frequently contain relics of animals 

 and vegetables ; indeed, in some instances, the whole 

 mass of a mountain appears to be little else than an 

 aggregation of animal relics. 



Of no rock is there probably a greater variety than 

 of limestone. It is said there are nearly two hundred 

 varieties of marble, all of which are limestone. The 

 deposits which do not bear the name of marble, probably 

 present an equal variety. Chalk is, strictly speaking, 

 limestone, as it is composed of the same ingredients, 

 and in the same proportion with the quarries wrought 

 for marble, and for the more common purposes of lime. 



The Housatonic range of limestone is perhaps the 

 most extensive in New England. It commences in 

 Milford, near the mouth of the river, and extends with 

 some intermissions quite to its head, and even beyond 

 to the St Lawrence river, if not into Canada. The 

 Stockbridge and Middlebury marble, are in this range. 

 In Bolton, and Boxborough, the town north, are da- 

 posits of moderate extent. In Smithfield, Rhode Island, 

 is a quarry, from which lime of the finest quality is pro- 

 cured in great quantities. In Stoneham, twelve miles 

 north of Boston, is a small deposit. This resembles 



