394 EUROPEAN AGRICULTURE. 



crop of the same kind can be grown on the same land ; but it 

 would be extremely interesting if the fact of such exhaustion, and 

 its extent, could be more particularly determined by a chemical 

 examination of the soil which has been cultivated. The beau 

 tiful theory of the great agricultural oracle of the day, that 

 certain mineral ingredients which are always found in the ashes 

 of plants, and which are carried off when these products are 

 removed, and, being essential to vegetation, require to be either 

 artificially replaced or supplied by a natural process, and that, 

 the land being suffered to rest, or applied to a different production, 

 the ordinary influences of air and moisture in decomposing the 

 rocks of the soil will renew the supply of these mineral elements 

 which have been removed, seems to offer the desired explana 

 tion ; and the experiments to which this theory has led, and 

 which, under its influence, are now going on in various parts of 

 the country, must presently determine it, and, what is better, 

 show its proper application, and greatly simplify the processes of 

 agriculture, reducing its expenses and giving comparative cer 

 tainty to its results. 



The operation of air and moisture upon the soil, the effects of 

 light, and electricity, and frost, upon vegetation, all admit to be 

 powerful ; but they are as yet only partially understood, and 

 present subjects of the most interesting inquiry. In the progress 

 of science, technically so called, we have much to hope for; but 

 in what it has already accomplished, enough has been gained to 

 quicken, but very far from enough to satisfy, the appetite. One 

 of the most eminent agricultural chemists of the present day, 

 Boussingault, second perhaps to no other, has said,* &quot;A great 

 deal has been written since Bergman s time upon the chemical 

 composition of soils. Chemists of great talent have made many 

 complete analyses of soils noted for their fertility ; still, practical 

 agriculture has hitherto derived very slender benefits from labors 

 of this kind. The reason of this is very simple ; the qualities 

 which we esteem in a workable soil depend almost exclusively 

 upon the mechanical mixture of its elements ; we are much less 

 interested in its chemical composition than in this ; so that 

 simple washing, which shows the relations between the sand and 

 the clay, tells, of itself, much more that is important to us than 



* Rural Economy, Law s edition, p. 266. 



