240 



On Agricultural Chemistry. 



combustion is restored at all to the soil, it is very much less 

 efficacious than it would be if accompanied by the substance of 

 the cane itself. In a well-regulated sugar plantation, non- 

 nitrogenous products constitute the only export from the soil. 

 Hie nitrogenous elements, which are rendered insoluble when the 

 juice is heated, should be carefully removed, and either restored 

 to the soil directly as manure or after being employed as food for 

 animals. 



The English farmer necessarily suffers an exhaustion of his 

 soil from the removal of various ingredients which have not place 

 in the constitution of sugar. In grain both nitrogen and phos- 

 phate are exported, both of which must be restored to the soil in 

 due course. We hear of plantations which formerly produced 

 many hundred hogsheads of sugar, now producing one-third the 

 quantity. This can arise from nothing but exhaustion of the soil. 

 It cannot be too generally known that the elaboration of carbon 

 bears a very constant relation to the supply of ammonia in the 

 manure. Every pound of sugar exported, and every pound of 

 the cane which is burnt, involve the necessity of a supply of 

 ammonia to the soil. Taking into consideration the immense 

 advantage which a tropical climate affords, and the comparatively 

 high price of the product, the cultivation of sugar offers advan- 

 tages for the profitable employment of skill and capital greatly 

 superior to any that our agriculturists can hope for. It would, 

 however, be injudicious and improper, in defect of actual experi- 

 ments, to attempt to lay down rules in detail for the application 

 of a principle regarding which, as such, little doubt may be enter- 

 tained. 



I now come to the action of manures, which are generally di- 

 vided into two classes — -organic and inorganic. Although this dis- 

 tinction is by no means satisfactory, I shall adopt it as being gene- 

 rally understood. Organic manures are those which are capable 

 of yielding to the plant, by decomposition or otherwise, organic 

 matter — carbon, hydrogen, oxygen, and nitrogen — constituents 

 which uncultivated plants derive originally from the atmosphere. 

 Inorganic manures are those substances which contain the m.ineral 

 ingredients, of which the ash of plants is found to consist. Most 

 of the substances employed as manures contain both organic and 

 inorganic substances. The greater portion of soils consist of 

 minerals in a greater or less state of decomposition, combined 

 with a small amount of organic matter. Every soil is capable of 

 yielding a certain amount of vegetable produce under the influence 

 of climate and season, without the assistance of manure : this may 

 be called its natural produce. The proportion would vary each 

 year, according to the amount of rain, the temperature of the 



