THE ELEMENTARY BODIES. 15 



entirely or leave an insignificant remnant behind; while 

 wood or flesh leaves but little more of earthy matter or 

 ash unconsumed. All that has disappeared of these sub- 

 stances consist generally of three of the elementary bodies, 

 and rarely of four; while of all agricultural products the 

 greater part, inclusive of the combustible and inconbusti- 

 ble portions together, is made up of no more than twelve. 

 The four bodies referred to are carbon, oxygen, hydrogen, 

 and nitrogen. The twelve consist of these four, and cal- 

 cium, chlorine, magnesium, phosphorous, potassium, sili- 

 con, sodium and sulphur. 



An acquaintance then with the most important four ele- 

 ments mentioned is indispensable to the farmer; for it is 

 quite impossible for him to comprehend the laws which 

 govern the operations of nature in the growth of plants, or 

 the reasons why he adopts certain processes in his farm work 

 to aid and facilitate these natural operations, without a 

 previous knowledge of the nature of these elements and 

 their reactions upon each other. And at the same time it 

 is of the greatest interest to him that he should have some 

 knowledge at least of the nature of the other eight elemen- 

 tary substances which enter more or less into the ash or 

 incombustible mineral portion of the plants which he cul- 

 tivates. 



A brief consideration of the properties of these four el- 

 ements which make up the organic constituents of plants 

 and of the eight which go to make up their inorganic sub- 

 stance, will lead the way for a study of the means whereby, 

 and the manner in which, they enter into the circulation 

 of plants and form their substance. 





