ANALYSIS OF SOILS. 21 



standard ; for differently constituted soil will produce 

 different crops advantageously : one farm produces fine 

 wheat, another barley ; others again the finest oats and 

 beans in the parish. To compound a soil of exact 

 chemical parts, so as to afford permanent fertility, is a 

 mere theory. Nature and circumstances may produce 

 a piece of land, that will yield unremitting crops of 

 grass, and we call it a permanently good soil ; but art 

 cannot effect this upon a great scale. A small field in 

 this parish always produces good crops; not in conse- 

 quence of any treatment it receives, but by its natural 

 composition ; consisting principally of finely pulverized 

 clay, stained with red oxide of iron, a considerable por- 

 tion of sand, and vegetable earth: but though I know 

 the probable cause of this field bearing such good 

 wheat, I cannot bring the surrounding and inferior ones 

 into a like constitution, the expense far exceeding any 

 hope of remuneration. Rudolph Glauber obtained gold 

 from common sand, but it was an expensive article ! 

 Temporary food for a crop may be found in animal, 

 vegetable, or earthy manures, but these are exhaustible ; 

 and when aliment ceases, the crop proportion ably di- 

 minishes. In one respect, chemical investigation may 

 importantly aid the agriculturist, by pointing out the 

 proportion of magnesian earth in certain limes used for 

 manure, and thus indicate its beneficial or injurious ef- 

 fects on vegetation. I should not like lime containing 

 20 per cent, of this earth ; but when it contains a much 

 smaller proportion,! should not think it very deleterious. 

 This earth acts as a caustic to vegetation, and, neither 

 being soluble in water, nor possessing the other virtue 

 of lime, diminishes the number of bushels used accord- 

 ing to its existence, and thus deprives the crop of that 

 portion of benefit : but after all, as Kirwan says, the 

 secret processes of vegetation take place in the dark, 

 exposed to the various and indeterminable influences 

 of the atmosphere ; and hence the difficulty of deter- 

 mining on what peculiar circumstance success or failure 

 depends, for the diversified experience of years alone 

 can afford a rational foundation for solid and specific 

 conclusions. 



