Bibliography. 189 



We need not therefore insist upon the utility of such works as the 

 Agricultural Chemistry of Liebig, and the still more practical treatise 

 of Prof. Johnston. The latter is addressed, not to the philosopher, nor 

 the student, but to the tiller of the soil himself. It consists of a series 

 of lectures, delivered before a society of practical agriculturists ; most 

 of whom doubtless possess little or no knowledge of chemistry or 

 geology. It was therefore necessary to begin with the simplest facts 

 and principles of these sciences, to employ the most familiar illustra- 

 tions, to use no unnecessary technical terms, and none at all without 

 previous explanation. In pursuance of this plan, Prof. Johnston has 

 produced a work of the most interesting and popular character, com- 

 pletely adapted to the end in view, and fully worthy of his reputation as 

 a chemist. The first part of these lectures, the only portion which has 

 yet been issued in this country, is devoted to a consideration of the 

 organic elements and parts of plants, the properties of the elementary 

 and compound bodies which enter into their substance, or contribute to 

 their growth and nourishment ; to the general structure and uses of the 

 several parts of plants ; their mode of growth, and the manner in which 

 their food is absorbed and assimilated. 



The second part, which we understand will soon appear, is to be de- 

 voted to the inorganic elements of plants, and to the study of the soils 

 from which these are derived ; the constitution, origin, and methods of 

 improving soils in different districts, and under unlike conditions, with 

 the general relations of geology to agriculture. The third, to the na- 

 ture of manures, their mode of action, &c. : the fourth and last, to the 

 results of vegetation, the nature, constitution, and nutritive properties 

 of different kinds of produce, especially in reference to their several 

 equivalents or powers of supporting animal life ; the feeding of cattle, 

 the making of cheese, &c. ; the constitution and differences of various 

 kinds of wood, and the circumstances which favor their growth. After 

 this general view of the plan and scope of the work, we think it quite 

 unnecessary to give an analysis of the eight lectures of which the pi'es- 

 ent portion is composed. In the first lecture, which is chiefly prelimi- 

 nary, the author bestows a few thoughts upon the importance of agri- 

 culture : 



" That art on which a thousand millions of men are dependent for their very sus- 

 tenance — in the prosecution of which nine tenths of the fixed capital of all civili- 

 zed nations is embarked — and probably two hundred millions of men expend their 

 daily toil — that art must confessedly be the most important of all ; the parent and 

 precursor of all other arts. In every country then, and at every period, the inves- 

 tigation of the principles on which the rational practice of this art is founded, 

 ought to have commanded the principal attention of the greatest minds. To what 

 other object could they have been more beneficially directed ? But there are pe- 

 riods in the history of every country when the study of agriculture becomes more 



