262 Address before the Aasociatioyi of Amei^ican Geologists. 



cal survey, yet, with sufficient time given to a geological chem- 

 ist, there can be no doubt but most vahiable 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, and a 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, aifords 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 decomposition. 

 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 vegetation, 

 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 organic 

 matter by one simple act of combustion. But more recent exper- 

 imenters have found, that the composition 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 it 

 is composed of several distinct compounds. But, in determin- 



