Part III.] OR POISONED BY VEGETABLE GROWTH ? 
181 
it, by comparison, they are enriched, while sur¬ 
rounding lands are denuded, even supposing 
aqueous denudation and deposit the same in 
both. So, in dry windy weather, when culti¬ 
vated lands are thoroughly cleansed, and broken 
finely for sowing, great quantities, even of soil , 
change places by wind, by which exposed spots 
are impoverished, and sheltered spots enriched. 
This denudation is visible; so is the deposit of 
leaves. There are spots on which leaves are 
never allowed to rest, and others which every 
year catch large quantities. Ponds fill up even 
in man’s short existence, and must be emptied 
if they are intended to serve as ponds. This 
happens whether ponds have a run of a stream 
through them, or a run of rain into them, or no 
run at all into them. In the last case aerial 
deposit will fill them, chiefly with leaves. But 
in all cases aerial deposit forms a great item in 
filling ponds. 
For the rest, my aerial fancy will be voted 
incredible, because it is invisible. Yet great 
effects come from causes which are not very 
visible; and some people would stare (and 
among them, perhaps, Professor Sedgwick), if 
you told them that the top of the same Hamp¬ 
shire hill is on one side moving to the German 
Aqueous denu¬ 
dation is uni¬ 
versal, and is 
not confined 
only to the 
lines of torrents 
and rivers. 
