344 



MARL. — GRANITE. 



to it when withdrawn. There is a kind of clay 

 produced by the decomposition of feldspar, which 

 closely resembles marl ; it is, however, easily dis- 

 tinguished by its not effervescing when mixed with 

 vinegar, oil of vitriol, or any other acid, as marl 

 does. This substance contains from 40 to 95 per 

 cent, of carbonate of lime, with a quantity of vege- 

 table matter, sand, phosphate of lime, and a trace of 

 magnesia. Its immense value as a fertilizing agent 

 wilt be noticed in the ensuing chapter. 



We have already described, at sufficient length, 

 perhaps, the localities of the green sand marl, which 

 forms a deposite*over nearly the whole southern 

 half of New-Jersey. It has been traced in many 

 places through the Atlantic States to Alabama, and 

 has lately been discovered by Professor Hitchcock 

 in Massachusetts, and by Dr. Troost in Tennessee. 

 The green marl of Massachusetts consists chiefly of 

 silex, alumine, and oxide of iron, and does not con- 

 tain potash like that of New-Jersey : hence there 

 is much doubt as to its possessing such powerful 

 fertilizing properties as that of the latter. This can 

 only be tested by actual experiment. The marls of 

 Virginia and the Middle States, however, are chiefly 

 of the miocene era, and composed of carbonate of 

 lime (mostly derived from shells), from 12 to 90 per 

 cent. 



Granite. — We have given so full a description of 

 the granite formation in the United States, that lit- 

 tle need be added in this place. For building pur- 

 poses, no country in the world possesses such an 

 inexhaustible quantity and vkrkty of granite rocks 

 as New-England ; none more durable in structure, 

 or beautiful in appearance. 



Of the Eastern States, Maine is pre-eminent for 

 the abundance and excellent quality of her various 

 granite rocks, which offer facilities for quarrying 

 and exportation unequalled by those of any other 

 part of the known world. Here all varieties are to 



