162 APPENDIX. 



vegetable, as oil vitriol, or muriatic acid would animals. In carbonates^ 

 the acid forms part of the food of plants. The alkaline geates are so 

 very soluble, that when alkalies, as ashes for instance, are freely used, 

 we lose a part, by its draining away, or in wet soils becoming too di- 

 lute. But a small dose produces all the beneficial effects of a large 

 dose of lime. We have in ashes, not only the alkali to solve geates, 

 but a very large portion of carbonate and phosphate of lime. Experi- 

 ments are wanting to prove the relative value of lime and ashes. I 

 should not deem it extravagant to say, that a bushel of ashes is equal to 

 a cask of lime. The alkalies and their salts act more powerfully than 

 any other substance, in solving and converting geine. Lime in all its 

 forms ranks next. These produce always decided beneficial effects 

 The alkalies never fail. Ashes show their effects at once, due to the alka- 

 line part, while their carbonate of lime produces more permanent effect. 

 Lime, from peculiar states of the soil, may not show any immediate 

 good result, but ultimately, this result is sure to follow. Permanent 

 barrenness never is produced by the free use of carbonates. It surely 

 follows the free use of all other salts, yet in small doses, they all and 

 ever act beneficially, wlienever their bases, combined with carbonic 

 acid, would be beneficial. 



But how do the elements of soil act? As I have stated in the report 

 of Professor Hitchcock, by forming galvanic batteries with the roots of 

 living plants. The most active element in the pile is the root. The 

 soil, like the rocks from which it is derived, is slowly acted on by at- 

 mospheric agents. The effect of this action annually is imperceptible. 



A single plant in one season will effect a greater amount of decom- 

 position of a given portion of soil, than that produced by all the atmos- 

 pheric agents in many years. The galvanic agency of plants is not 

 confined to the soil, in immediate contact with their roots. It extends 

 from these, in every direction, to undetermined distances. Hence there 

 is a transfer, as is usual in galvanic decompositions, of substances quite 

 remote from the plant. The whole plant contributes to this galvanic 

 agency. It never exists in full force, perhaps not at all, till the plant 

 has pushed above ground — acted on by air and light. 



The soil, as we have explained, consists almost wholly of silicates, 

 though it has been proved, that carbonic acid slowly decomposes these, 

 and an argument, for the mutual action of the elements of silicates, 

 derived from their admitted electrical states, yet the amount of this ac- 

 tion is never measurable in one season. Being silicates, they have no 

 tendency to act on each other. We can only excite this action by in- 

 troducing new elements, salts, which in this sense only, can be said to 



