352 MASSACHUSETTS AGRICULTURE. 



and the published result of its experiments would have its due 

 wei<2,lit with the public. 



But this is not the only line of investigation with reference to 

 chemical farming. The mixing and compounding of different 

 Boils, after ascertaining their nature by chemical tests, is a curi- 

 ous subject of inquiry, which may lead to important results. 

 There are some ingredients which improve the soil when applied 

 to it, and yet evidently impart none of their substance to the 

 crops that are improved by it. What is the nature of the benefit 

 they yield to the soil ? Take charcoal for an example. Is this 

 substance simply hygrometric in its action as a fertilizer ; or is 

 it also a chemical absorbent dni^ fixer of certain volatile matters 

 which are useful to plants ? Why is plaster useful as a fertilizer 

 of certain upland soils ? Does it supply the soil with a chemical 

 ingredient that constitutes a part of the food of plants ; or is 

 this substance simply hygrometric, and does it act by retaining 

 moisture in a condition that renders it available to the roots of 

 plants, while it is not liable to be confronted by the sun and 

 atmosphere ? 



It is needless to multiply these queries, which might be indefi- 

 nitely extended. A few leading questions will nevertheless seem 

 to point out the direction which a philosophical experimenter 

 might be disposed to follow. It is important to learn by experi- 

 ment to distinguish between these substances which act by 

 fixing and retaining volatile matters, that enter into the organi- 

 zation of plants, and those, on the other hand, that are the 

 immediate food of plants. Among the former, charcoal may be 

 classed ; for though carbon is an important part of vegetable 

 nutrition, it cannot be supplied to vegetation in the form of 

 charcoal. To be rendered available to plants it must be in a 

 gaseous or in a liquid form, like carbonic acid and carbonic 

 acid gas. 



13. Tlie art of preserving our crops and other vegetation 

 from the devastations of insects, is one of the most important 

 that can occupy the attention of the cultivator at the present 

 day. There are some species of noxious insects which have 

 increased to an alarming extent, within a few years, and that 

 seem to multiply with greater rapidity than the agents employed 

 by nature, to check their over-multiplication. Birds are gener- 

 ally supposed to be the the most useful of all these checks. 



