292 TRANSACTIONS OF THE 



lations of Chemistry to Agriculture, in which he lays down in 

 fifty propositions a digest of the whole scheme of agricultural 

 science, reminds me of a paper which I had prepared some 

 months since as a compendium of all that I had learned in fifteen 

 years reading and study of the subject. 



All that has been written or said upon the action of manures 

 as food for plants is reducible to the following propositions : 



1st. Condition of all manures to be appropriated by plants is 

 solubility. You may spread animal charcoal over the soil by 

 tons, and plants will derive but little phosphoric acid therefrom. 

 Pulverise the Feldspar rock to powder and its potagh will not be 

 yielded up to the tender radicles of plants. If your field con- 

 tains y\^o <^f silex, your corn and wheat may never mature for 

 want of silica. The animal charcoal must become superphosphate 

 by the action of sulphuric or carbonic acids. The Feldspar must 

 be changed to Carbonate of Potash by chemical decomposition. 

 Silica must be reduced to Silicic acid or a Silicate of some alka- 

 line base, before plants with their delicate appetites will taste 

 them. I have put eight tons of animal charcoal, or Phosphate 

 of Lime upon an acre without perceiving the least benefit, while 

 I have dissolved 150 lbs. of the same in an equal quantity of 

 Sulphuric acid to which was added fifty lbs. of guano, and ap- 

 plied it with surprising effect. 



2d. Durability or Solubility, by its very essence becomes a 

 very tempor.".ry condition of the soil, unless the latter contains 

 such elements as will retain soluble or dissoluble food of plants, 

 or such as will but slowly prepare it by chemical change to be- 

 come soluble in only sufficient quantity for their use. Upon a 

 porous sandy soil, you may pour the richest elements of vegeta- 

 tion in profuse abundance and they will need constant renewal. 

 Each year of enrichment leaves nothing for the next. But give 

 that ever hungry soil (that like the horse leaches' daughters, cries 

 always, give, give,) a fair proportion of carbonaceous matter in 

 the shape of prepared peat, or charcoal dust, or of aluminous 

 matter in well divided and pulverised clay, and its hunger is 

 easily appeased; it will retain for ages something of all Avhich 

 you may give it. 



3d. The third condition of manures is communication, or com- 

 plete mixture with the particles of soil. No amount of the rich- 

 est manures will produce the maximum of vegetation, or even 

 mediocrity, if the soil to receive them is not rendered pulveru- 

 lent by tillage, and the manure reduced to its finest divisibility 



