262 Address before the Association of American Geologists. 
cal survey, yet, with sufficient time given to a geological chem- 
ist, there can be no doubt but most valuable ultimate results 
would follow his labors. 
Although the science of agricultural chemistry had a vigorous 
commencement in the labors of Davy and Chaptal, yet its subse- 
quent progress has not been correspondently rapid; and it must 
yet be regarded as in its infancy. Hence too much has been ex- 
pected from the analyses of soils in our country, anda conse- 
quent disappointment has been felt. Distinguished chemists are 
not yet agreed in respect to some of the fundamental principles 
of the science. The recent able work by Prof: Liebig on organic 
chemistry, affords evidence of the truth of this statement in the nu- 
merous new views which it presents, and which he declares to be 
different from those usually maintained. Many of these views 
will be adopted at once, as original discoveries ; but in regard to 
others, it is not to be expected that chemists will receive them 
without discussion. With Raspail he maintains, that plants are 
nourished solely by the absorption of carbonic acid from the at 
mosphere and from soil; whereas, the prevailing opinion is, that 
they derive their support partly from carbonic acid and partly by 
the direct imbibition of organic matter in some of the forms of 
humus, by their roots. ‘He supposes that the humus acts no 
other part than to furnish carbonic acid by its decompositiol- 
Others maintain that some of it is taken up in a state of solution, 
by capillary attraction, or by galvanic action. And as all chem> 
ists were not convinced by the arguments of Raspail, they may 
not be satisfied with the more able reasoning of Liebig, on the 
same subject. His views of the*agency of nitrogen in vegetable 
nutrition,—his discovery of ammonia in the atmosphere, and his 
_ many new views respecting the agency of salts upon vegetations 
and on other subjects, will render this work a most valuable ad- 
dition to agricultural chemistry. ” 
The earlier agricultural chemists laid by far too much stress 
upon the mineral constitution of soils, and disposed of the orgame 
atte ne simple act of combusti But more recent expe 
_— found; that th 1position and condition of the or 
ganic matter are of the highest importance in relation to vegeta 
tion, and they have made great efforts to ascertain the true 
character of mould or humus. [It is agreed on all hands, that 
