233 
admission by the roots in the form of humate of ammonia, 
and that this substance is the vehicle by which carbonaceous 
matters, as fermented straw, &c., are rendered available 
and useful to vegetation. 
The carbonaceous matter of manures also gains admission 
by the means of the earths and alkalies found in the ashes of 
plants, in the form of humate of lime, potash, soda, and 
united with the oxide of iron and manganese. 
To show that no mean quantity of carbon does enter 
from the soil by means of humic acid, take wheat as an ex- 
ample, which, from Boussingault's table of the composition of 
cultivated substances, consists of 46.1 carbon, 2.3 nitrogen, 
2.4 ashes; according to Rigg, averaged at six different periods 
of its growth, of 39.4 carbon, 2.5 nitrogen, and 3.3 residual or 
earthy and saline ingredients, and which residual, according 
to Davy, consists of 47 per cent, of silica and earthy 
phosphates, and the remaining 53 per cent, of lime, potassa, 
soda, oxide of manganese and iron, which two last have the 
same capacities of saturation with humic acid which lime 
has ; the equivalents of lime being 28, potash 48, soda 32, 
nitrogen 14, ammonia 17. 
Take Boussingault's analysis : wheat consists of carbon 
46.1, nitrogen 2.3, and ashes 2.4 — from which ashes deduct 
47 per cent, for silica and earthy phosphates which do not 
combine with humic acid, and there will be 1.3 of ashes. 
According to Mallagutti's formula of humic acid, and 
which agrees with Boullay, (see Thomson's Chemistry, — 
Ulmic Acid,) the atomic weight is 315. 
Or 30 atoms of carbon 180 or per cent. 57.15 
15 5, hydrogen 15 „ 4.76 
15 „ oxygen 120 „ 38.09 
315 100. 
Therefore, as 14 (the atomic weight of nitrogen) is to 
315, (the atomic weight of humic acid,) so is 2.3 of nitro- 
D 2 
