58 
COURSE OF THE SAF. 
[Part IT. 
according to the different soil in which it is 
grown. Any one of these three facts proves 
that the potato is nourished from the soil, not 
from the air: and under this idea the soil is 
twice hoed after the potatoes are above it; that 
is, it is ‘ Hat hoed ” and hilled up.” And 
Liebig himself says: “ The increase of crops 
obtained by the use of guano is very remark¬ 
able. According to the same authority (Garci- 
laso), the crop of potatoes is increased forty-five 
times by means of it,” and “ I applied to a field 
of potatoes manure consisting of night-soil and 
sulphate of magnesia (Epsom salts), and obtained 
a remarkably large crop.” Again : “ In the first 
year all the different parts of the field produced 
potatoes, but they succeeded best in those di* 
visions which had been manured with peat, 
ashes, lime, and marl.” All these cases prove 
the growth of the potato to be from the soil, not 
from the air. 
If plants draw their nourishment from the 
atmosphere, why do we find plants peculiar 
to peculiar soils ? Let any one farm on the 
idea that the growth is to accrue from the 
atmosphere, not from the soil. If Liebig’s 
views are correct, a landlord should put his 
land up to let, not by the quality of the land, 
