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 proportionably 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, I 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. 
