18 INTRODUCTION. 



nature, and to do so, as far as possible, with- 

 out the unnecessary use and encumbennent of 

 scientific terms or expressions. In .carrying out 

 this design, the simplest plan appeared to be, 

 to treat successively the chemistry of the earth, 

 the air, and the ocean ; by which means, almost 

 all that is of importance to be learned of the 

 chemistry of nature, will come simply and 

 naturally under discussion. Such a notice of 

 the general principles of the science, as is re- 

 quisite to render the subsequent pages free from 

 difficulty, is added by way of a prefatory section 

 to the chemistry of the earth. 



