ON THE CULTIVATION OF THE EARTH. 63 



carried on ; and by what means these elementary 

 principles or substances are collected, com- 

 bined, put into action, and appropriated or dis- 

 posed of; and likewise, the composition or con- 

 stitution, and properties of the eartli, and the 

 manner in which it contributes to the formation 

 and sustenance of vegetables. To accomplish 

 these things, some of the most eminent chemical 

 philosophers of the age have given their attention, 

 and a very comprehensive little work on the sub- 

 ject has been published by Mr. Kirwan. 



Sir Humphry Davy was also induced by the 

 Board of Agriculture, to give to the public a 

 regular course of lectures on agricultural che- 

 mistry ; and as those two eminent professors 

 have in their works, given the subject a full at- 

 tention, and considered it in all its various parts, 

 and their authority being generally respected 

 and relied upon, I shall confine my observations 

 and reference, on this part of my subject, chiefly 

 to them. 



Sir Humphry Davy justly observes, ** It is 

 " scarcely possible to enter upon any investiga- 

 ** tion in agriculture, without finding it con- 

 *' nected more or less with doctrines or elucida- 

 " tions derived from chemistry. 



" If land be unproductive, and a system of 

 " ameliorating it is to be attempted, the sure 

 " metliod of obtaining the object is by deter- 



