MlNfiRALS. 



401 



a mountain, in the township of Grafton, about twenty 

 miles eastward of Dartmouth college. 



The scarcity of glass during the American war, 

 brought this mica into repute. Many persons em- 

 ployed their time in blowing the rocks, and sepa- 

 rating the laminx, cutting them into squares, and 

 vending them about the country. This substance is 

 particularly valuable for the windows of ships, as it 

 is not brittle but elastic, and will stand the explosion 

 of cannon. It is also used to cover miniature paint- 

 ings, and to preserve minute objects for the micros- 

 cope. The disadvantage of it for windows is, that it 

 contracts dust, and is not easily cleaned; but for 

 lanterns, it is preferable to glass.* 



For magazine lanterns it is particularly valuable, 

 as it will not crack by the falling of a candle against 

 the sides, an accident which has often occasioned 

 great mischief on board ships of war. 



Near Philadelphia the rocks of granite are inter- 

 spersed with mica, and large strata of it are fre- 

 quently met with, of no determinate figure or size. 

 In New York red feldspar forms huge masses of red 

 granite. 



Clays,, ..The United States abound with a variety 

 of excellent clays, proper for even fine wares. In 

 North Carolina, a large body is said to have been 

 found before the revolutionary war, some of which 

 was taken to England, and highly approved of by 

 Mr. Wedgwood.t Marie abounds near Mount Holly. 



* Belknap. 



t A specimen of this clay, with an account of the soil near which it 

 is found, would be highly acceptable to the author, who regrets that 

 his iijformation with respect to the place where it is to be found is 

 to deficient. It is said %o be found near Halifax, North Carolina* 



