Action of the Atmosphere upon newly-deepened Soil. 437 



of mineral salts into the plant. Phosphate of lime, phosphate 

 of magnesia, and silica, can by the aid of carbonate of ammonia 

 become somewhat soluble and absorbable. Every soil contains 

 carbonate of lime, which is rarely free from alkalies, and this 

 under the influence of solar heat will decompose sal-ammoniac 

 and sulphate of ammonia, by which means soluble salts of lime 

 and carbonate of ammonia are produced." ( Coinptes Rendus, XVII. 

 1118.) 



Some of the mineral constituents of plants are dissolved in the 

 soil only by water containing carbonic acid or some salt of am- 

 monia. That the nitric acid and ammonia of the atmosphere 

 probably exercise some solvent power upon the mineral matter 

 of the soil, the experience of Mr. Lawes and others shows, for the 

 produce of nitrogenised matters in the crop are not porportional 

 to the supply of nitrogen given to the soil in the shape of am- 

 moniacal manures, there being a disappearance of ammonia in 

 some manner which perhaps can be accounted for most feasibly 

 on the supposition that it acts as a solvent uptm the mineral 

 matter of the soil, and thus is the means of introducing into the 

 plant those necessary substances which might without it remain 

 in an insoluble form. It would, indeed, seem that this dissolv- 

 ing power of ammonia upon the silicates, phosphates, and other 

 eartliy matters of the soil, is perhaps a more important property 

 than its use merely as a supplier of nitrogen, for the amount of 

 it withdrawn from the soil is sometimes four times as much as 

 appears in the crop. 



Nitric acid and ammonia have been spoken of together, as 

 their action is probably similar, both as regards the soil and the 

 crop growing upon it, and they niay likely replace each other in 

 those respects. 



When it is considered that many of the nitrogenised consti- 

 tuents of the crops seldom find their way into the dung-heap, 

 but are sent off the farm in the grain and live stock sold, and that 

 nitrates and ammoniacal manures are expensive articles to pur- 

 chase, then the amount of these ingredients of the atmosphere, 

 as available sources of nitrogen to tlie soil and the ]dants that 

 grow upon it, becomes a very interesting inquirv ; for if it can 

 be shown that, by certain not too expensive modes of manage- 

 ment, the surfaces of oiir fields can be made to catch enough of 

 these substances for the wants of eacii crop, a gi'eat advantage 

 would be gained, and a standing diniculty be removed. Liebig, 

 in a recent publication, writes, " I consider mvself as perfectly 

 justified in concluding from my experiments, that on ordinary 

 farms, provided we give to the soil the proper phj/siat/ ijiuditi/ 

 and composition, there may be, by degrees, such an amount of 

 ammonia collected, or condensed from the atmosphere, as to be 



