832 
the seed which leads to the separation of one or more 
of its constituent parts? They are essentially heat 
and moisture ; for it is only when the seed is duly 
moistened, and placed in a proper temperature, that, 
either by decomposition or by germination, it is able 
to emit' carbon. By a high degree of heat alone, in- 
deed, the carbon of the seed may be separated and 
expelled ; but the results are then altogether different 
from those which follow the spontaneous changes to 
which we have alluded, and to which the concur- 
rence of moisture is necessary. Since, therefore, 
heat cannot be the sole agent by which the carbon 
of the seed is brought into a state capable of combin- 
ing with the oxygen gas of the air, no other mode oc- 
curs to us in which this can be accomplished, but 
that of solution in water ; and, therefore, we conclude 
that this carbon passes off with the moisture of the 
seed, or is, at least, brought into a state capable of 
doing so by its solution in that fluid. 
636. To this conclusion it has been objected, that 
carbon is not soluble in water, because pure charcoal 
appears to resist the solvent power of that fluid. 
However much this objection may weigh against the 
solubility of pure carbon, it does not apply to carbon 
as it exists in vegetables, where the complex state of 
its combination may greatly facilitate its solution. 
For " in chemistry," says Dr Thomson, " it may be 
considered as a truth, to which at present few or no 
exceptions are known, that bodies are decomposed 
with a facility inversely as the simplicity of their 
composition ; those which consist of the fewest in- 
gredients being decomposed with the greatest diffi- 
