INTRODUCTION. . 19 



rocks and simple minerals, the character of the soil. As all 

 soils originate from the decay of rocks, if we know what rocks 

 are crumbled into soil we may determine with some degree 

 of probability its character, and what agencies are at work to 

 benefit or injure the expected crop. If by a simple inspection 

 of the mineral ingredients of a soil, we may determine what 

 crop will best flourish upon it, we certainly must regard the 

 aid not only seasonable, by preventing us from expensive ex- 

 periments, but also highly valuable, by enabling us to obtain 

 a greater quantity of productions. So great is the aid which 

 geology renders to agriculture, that one branch of it, the origin 

 and descriptions of soils, is called by one writer (Hitchcock), 

 "Agricultural Geology." Geology further aids agriculture 

 by pointing out the location of useful manures, such as veg- 

 getable matters, lime and plaster. 



II. Chemistry offers greater aid by far, to agriculture 

 than any other science, because it explains those changes 

 which must take place in the vegetable organs, and in the 

 soil, by which the processes of vegetation are carried forward ; 

 that is, chemistry supplies the greater number of the condi- 

 tions and agencies which are requisite to the highest activity 

 of the vital functions of plants, and hence teaches us how to 

 obtain, with the least expense, both the largest quantity, and 

 the best quality, of products. So great is its importance, 

 and so far does it exceed all other branches of knowledge, in 

 its relation to agriculture, that the terms '' Agricultural 

 Chemistry" (Davy), " Chemistry of Agriculture" (Liebig), 

 "Chemistry applied to Agriculture" (Chaptal), have been 

 employed as titles of the most important works, in which at- 

 tempts have been made to apply the principles of science to 

 this art. 



It may be necessary, however, to point out, in a general 

 way, some of the specific forms in which this science may be 

 useful to agriculture, both for the sake of illustrating the gen- 

 eral nature of the subject, and its importance to the farmer. • 



