117 
getable economy, must be considered as of less 
importance, particularly in their relation to agricul- 
ture, than the other principles ; and as it appears 
from M. de Saussure’s table, and from other ex- 
periments, they differ in the same species of ve- 
getable when it is raised on different soils. 
MM. Gay Lussac and Thenard have deduced 
three propositions, which they have called laws 
from their experiments on vegetable substances. 
The first is, “ that a vegetable substance is always 
acid whenever the oxygene it contains is to the 
hydrogene in a greater proportion than in water.’ * 
The second , “ that a vegetable substance is al- 
ways resinous or oily or spirituous whenever it con- 
tains oxygene in a smaller proportion to the hydro- 
gene than exists in water.” 
The third , “ that a vegetable substance is neither 
acid nor resinous, but is either saccharine or muci- 
laginous, or analogous to woody fibre or starch, 
whenever the oxygene and hydrogene in it are in 
the same proportions as in water.” 
New experiments upon other vegetable sub- 
stances, besides those examined by MM. Gay 
Lussac and Thenard, are required before these in- 
teresting conclusions can be fully admitted. Their 
researches establish, however, the close analogy be- 
tween several vegetable compounds differing in 
their sensible qualities, and combined with those of 
other chemists, offer simple explanations of several 
processes in nature and art, by which different 
vegetable substances are converted into each other, 
or changed into new compounds. 
i 3 
