157 



[D.] 

 Letters from S. L. Dana, M. D., on Ashes, Lime, &.c. 



LETTER I. 



Lowell, February 16, 1839. 



Dear Sir, — You have asked me how the action of ashes, leeched, 

 or unleeclied, whether of wood, peat, or coal, is to be explained on 

 my views of vegetation. The best answer I can give you, is to state 

 what is the composition of ashes, and to glance at my views. By the 

 last, I presume you refer to statements in Prof. Hitchcock's late re- 

 port. I have there said that fertility depends on salts and geinc. 

 Without the last there is no healthy vegetation. The great body of 

 the soil, in which salts and geine act, is only the comminuted remains 

 of rocks, usually called primitive. We have termed this "granitic 

 sand." We have thus three great, natural divisions of the ingredients 

 of soil : 1st. Geine, 2d. Salts, 3d. Granitic Sand. Strictly speaking, 

 we have two classes only, geine and salts, for the "granitic sand" is a 

 mass of suits ; a mass, in which silex acts as an acid, and alkalies, lime, 

 magnesia, alumine, metallic oxides as bases, a mass o{ silicates. I pre- 

 fer this term to granitic sand, and I shall heieafter use it. Let us now 

 glance at these three divisions. 



1. Geine. — To my remarks, already published by Professor Hitch- 

 cock, I now add, that geine enters vegetables simply as geine, or as an 

 alkaline, earthy, or metallic geate, dissolved either in water or in alkali. 

 The organic and inorganic acids and salts of the plant, decompose 

 these varied forms. The elements of geine, its oxygen, hydrogen, and 

 carbon, play their usual part in vegetable economy. Acetic, and prob- 

 ably some of the other vegetable acids, do not precipitate the alkaline 

 solution of geine. In this case, it may still circulate in fluid form in 

 plants. The earthy and alkaline bases of the geates form the bases of 

 the various salts which plants afford. 



2. Salts. — This class includes, first, compounds of geine ; second, 

 alkaline -salts, potash, soda, ammonia, and all their combinations, 

 known by the names of carbonates, sulphates, nitrates, muriates, &.C., 



