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ultimatel}-, from the herbage of the ground, vegetable physiology has still 

 more impoiiant aid to render to every form of practical agriculture — deter- 

 mining the functions of the root, as imbibing the food of the plant, in water}"- 

 solution; of the stem, with its organs of circulation; of the leaf, which 

 retains and assimilates what is necessary to the structure of the whole and the 

 character of the fruit, discharging into the atmosphere the superfluous matter in 

 the shape of gases and vapor. 



The philosophy of each of the imponderable agents, light, heat, electricity, 

 and magnetism, has relations to vegetable life and health of an interesting and 

 important character. 



But of all the sciences, chemistry is the most fruitful in the aids it is destined 

 to render to agriculture. By the analysis of the laboratory, we are put in pos- 

 session of all the chemical elements of the vegetable kingdom, both those that are 

 common to all plants, and those that distinguish one species from another. We 

 are thus enabled to infer the composition of soil adapted to each plant ; and by 

 the analysis of a given soil, we ascertain the elements in defect, which it is the 

 office of good husbandry to supply. 



This leads us to the doctrine of specific manures — the basis of extensive 

 improvements, made, and to be made, in practical agriculture. 



Farmers have observed that some crops exhaust a given soil more rapidly than 

 others. Chemistry detects the elements abstracted from the soil by the annual 

 crop, and directs to the specific manures which will replace these elements, and 

 keep the land in heart. Without the science, the land may be condemned to 

 lie fallow, or to be recovered by the empirical and wasteful application of 

 manures, in .the grosser forms. 



For example, tobacco, the vine, the pea, and clover, require lime in large 

 quantities ; and as the supply comes to the plant through the root, a succession 

 of crops will soon exhaust the soil, unless that element be replaced by the hand 

 of the farmer. 



It cannot be doubted that every physical element found in the plant must 

 have had its previous existence in the soil, or the atmosphere. " It is upon the 

 clear undei-standing of this fact," as an English writer well remarks, "that the 

 successful business of the farmer depends. It is calculated to raise the operations 

 of the agriculturist to a level with those of the manufacturer; and instead of 

 committing the cultivation of the soil to accident, as if nothing were understood 

 respecting it more than the mechanical preparation of it for the seed, it will 

 serve to explain upon what causes growth and production, and consequently 

 their opposites, abortion, and non-production, fundamentally depend, and 

 of course, will enable him to provide against both." All this is well said, and 

 presents the valuable thought very clearly to the apprehension of the farmer. 



