502 [Assembly 



IV. Tlu Salts. — From the small quantity in which these exist in 

 the tissues of plants, I hardly knowwhether to class them as food or 

 as medicine ; yet in these days, when the limit between the two clas- 

 ses is becoming daily more indistinct, we may rank them as food. 

 We are apt to associate their existence in the wood of the plant, with 

 the condition in which Ihey exist after complete combustion as 

 ashes. Prof. Rose, of Berlin, has shown that there is but little 

 analogy, that ashes are the result of the complete oxydation of 

 the inorganic portions of the plant, while the heat of combustion, 

 if the supply of oxygen is limited, sublimes and dissipates these 

 elements with its smoke. It is well known that close stoves make 

 less ashes from the same wood than open ones, and that little or 

 no ashes is produced by the combustion of charcoal. On the one 

 extreme then, there are no ashes in wood, as every wood-chopper 

 knows, while at the other extreme, ashes may b:~ melted into 

 glass, as ev^ery body has heard. It does not follow then, that 

 when we have furnished the earth with the ashes that we have 

 obtained by burning one tree, that we have furnished the mineral 

 matters necessary for the growth of such another. It does not 

 follow any more certainly, than if we had furnished an equal 

 weight of pounded glass, and the claims of all the mineral 

 manures must be referred back after all to the tedious details of 

 extended observations. Prof. Rose has shown that these inorganic 

 substances undergo processes of reduction in the plant, and of 

 oxydation in the animal, as food does, and that they are generally 

 most soluble in the oxidized condition; yet the refuse of the 

 leaches of asheries lies exposed to the weather for years undis- 

 solved, and ashes applied to the soil must to a great extent do the 

 same thing. Yet they do slowly dissolve, for they are well known 

 to be a very permanent and lasting manure. 



When we consider the small percentage of mineral matter that 

 go into the composition of a plant, we must not conclude as some 

 have done, that it is only necessary to furnish these to a barren 

 soil to furnish two pounds of the ashes of wheat, in order to obtain 

 one hundred pounds of grain. Indeed, if the ashes were perfectly 

 soluble, and if every element of organic food were present, this 

 result would not occur. Experience has shown that the aggre- 

 gate amount of salts in the soil, must be many times greater than 



