465 
Nutrition of Vegetables . 
part of the air, explain the formation of those vast mines of pit- 
coal, which still retains the marks of those organized substances 
whence it originated, and the organic origin of which is suffici- 
ently announced by its composition of carbon, hydrogen, oxigen, 
and azote l But without appealing to these ancient productions 
of the vegetable kingdom, buried in the earth in such abundance, 
we need only cast an eye on its surface, to satisfy ourselves that 
nature must have taken other steps to produce carbon. 
On the other hand, if, in the silent progress of vegetation, the 
elements of water concur with the solar light to produce char- 
coal by intimate combinations unknown to us, charcoal ought to 
contain hydrogen likewise ; and this is confirmed by experience. 
If charcoal strongly calcined be urged in the fire with a sub- 
stance that has an affinity for hydrogen, the charcoal is partly 
decomposed, and hidroguretted products are obtained. Mr. Ber- 
thollet mixed 30 gr. [460 grs.] of charcoal calcined in a forge 
fire with 20 gr. [309 grs.] of sulphur, and by distillation in a 
porcelain retort obtained more than 100 cubic centim. [391 lines] 
of sulphuretted hydrogen gas : and it appears to me to be pro- 
bable, that if the experiment were frequently repeated with the 
same charcoal, it might be totally decomposed, a fact that it would 
be interesting to verify. 
If oxigen in the state of gas be presented to the charcoal in- 
stead of sulphur, water is formed, as is proved by the experi- 
ments of Lavoisier on the combustion of charcoal, as well as by 
those of Mr. Hassenfratz : and analogous results are obtainable 
with metallic oxides, according to the observations of Cruikshank. 
It even appears from the nice investigations of Messrs. Biot 
and Arrago on the refractive power of bodies, that the diamond, 
which has hitherto been considered as pure carbon, must con- 
tain a large quantity of hydrogen, which has the greatest refrac- 
tive power of any substance yet observed in nature. These gen-^ 
tlemen intend to verify their conjecture by direct experiments, 
from which very interesting results may be expected. The ex- 
istence of hydrogen in the diamond has been announced from 
©ther facts by Mr. Winterl. 
From the chief facts that have been here mentioned, it follows ; 
a great deal of hydrogen. Does not this fact indicate something common 
between hydrogen and light, particularly when we observe, that these two 
fluids, the lightest in nature, seem likewise to produce analogous effects on 
#©me metallic oxides and salts i 
