175 



CHAPTER XV 



CONNECTED RECAPITULATION OF THE VARIOUS 

 TOPICS TREATED IN THE PRECEDING CHAP- 

 TERS. 



We have now gone over nearly all of the ground 

 that I have thought it advisable to traverse, in a trea- 

 tise of this character. It may be of advantage, id 

 closing, to give a condensed view of the whole sub- 

 ject, recapitulating the main points that have been 

 illustrated and explained. 



This will serve as a species of index, and will, at 

 the same time, recall such arguments and facts rela- 

 tive to the various divisions indicated, as may have, 

 been forgotten. 



CHAPTER I. 



The art of cultivating the soil ; what this is, in its 

 proper meaning. 



Plants. Great division of them into organic and 

 inorganic substances. Organic bodies burn away ; 

 inorganic bodies incombustible. 



Names of organic bodies : carbon, hydrogen, nitro« 

 gen, oxygen. 



Carbon, a solid, of which charcoal, plumbago, and 

 the diamond are forms. Hard, and combustible. 



Hydrogen, a gas, colorless, tasteless, inodorous, the 

 lightest body known. Inflammable, explosive when 

 mixed with air, extinguishes combustion, and will 

 not sustain life. 



