208 
ARE SOILS ENRICHED, IMPOVERISHED, [Part III. 
every year on the same land, and ploughed in 
before ripening, the land would be enriched, not 
impoverished ; that is, a great increase of car¬ 
bonic acid would probably occur from vegetable 
chemistry, and a great increase of the inorganic 
constituents of plants from disintegration. In 
fact, although bearing wheat every year, the 
soil would become as rich as maiden soils 
always are. A process resembling this is what 
does go on in natural forests, in addition to 
the absence of denudation. In the case which 
Lyell mentions, of bogs formed “ by the fall of 
trees and the stagnation of water caused by their 
trunks and branches obstructing the free drain¬ 
age of the atmospheric waters, and giving rise to 
a marsh,” and “ of mosses where the trees are all 
broken within two or three feet of the original 
surface, and where their trunks all lie in the 
same direction,” it is not the trees which are dy¬ 
ing out on soils that have “ become exhausted 
for trees” which break or blow over in wind; 
but, on the contrary, the trees which break or 
blow over in wind are the rank product of a soil 
which suits them, and which grows them too 
close to have side-boughs, and consequently too 
tall for their girthing and for their circum¬ 
scribed roots. Many countries have ceased to be 
