INTRODUCTION. 25 



their preservation and use, with the diseases which attack 

 them. 



Plan of the Work. 



I. In accordance with the above views, the first three 

 chapters are devoted to the conditions of the life of plants, un- 

 der the general head o^ Biology, including all the agents that 

 influence the processes of vegetation, the character, composi- 

 tion, source and assimilation of the vegetable principles. 



II. The next four chapters are devoted to the composition 

 of the rocks ; origin and classification, composition and im- 

 provement of soils; with the theories of the action of ma- 

 nures, rotation of crops, fallow crops, and practical sugges- 

 tions. 



III. The closing chapter explains the processes of Horticul- 

 ture, with the application of those principles which are par- 

 ticularly connected with this important branch of agriculture. 



The object of the work, then, generally, is to explain the 

 phenomena of vegetation, and to deduce practical rules for 

 the benefit of the practical farmer ; in order to render the 

 modes of tillage more precise and rational, and thus to afford 

 a stimulus to intellectual and moral improvement, by making 

 farmers more scientific men ; and in order to increase the 

 amount of agricultural productions, by rendering the earth 

 more fertile, and the processes of cultivation easier and more 

 successful. 



If by the application of the principles contained in this 

 work, these results are attained, in but a slight degree, it is 

 all that I can hope. I will therefore conclude these intro- 

 ductory observations by a calculation of the value of any 

 slight improvement in this most useful art. 



In England, " the average produce of wheat," says Mr. Pu- 

 sey, " is stated at 26 bushels per acre ; if by a better selection 

 of seed we could raise this amount to 27 bushels only, (a sup- 

 position by no means unlikely), we should by this apparently 



