33 



The larger portion of the soils of New England, 

 as stated by the honorable gentleman, is undoubtedly 

 derived from granite and other primary rocks ; and 

 many of the red sandstone soils, such as those in the 

 neighborhood of New Haven, are, in fact composed 

 of the principles found in granite rocks. Argillace- 

 ous soils, or those which are derived chiefly from the 

 decomposition of argillaceous or clay slate, abound 

 likewise in many parts of New England and of Mas- 

 sachusetts, and being retentive of water, are found 

 highly productive in grass and grains. 



A considerable part of the nutriment of plants is 

 undoubtedly derived from the air, and water, or its ele- 

 ments, constitutes a large portion of their food. The 

 composition of water is now well understood, and we 

 may with safety, in the presence of this intelligent as- 

 sembly, speak in technical terms of the constituent 

 parts of water, hydrogen and oxygen, which enter 

 largely into all vegetables. Carbon, which forms 

 also a large part of all plants, though it exists in com- 

 paratively small proportions in the form of carbonic 

 acid gas in the air, is yet derived from innumerable 

 sources and supplied to the growing vegetables in 

 abundance. The effect of light upon the green 

 leaves of plants is to decompose the carbonic acid, 

 and the carbon is absorbed to nourish the plant, 

 and the oxygen is evolved into the air ; thus it 

 separates from the atmosphere an important element 

 of nutrition, supplying it in the form of food for the 

 plants. 



Mr. Silliman farther alluded to the curious fact in 

 the constitution of nature, that notwithstanding the 



