I -j TIIK IT.AXT. 



in other words, we must take them apart, and exam- 

 ine the different pieces of which they are made up. 



If we lurn any vegetable substance it disappears, 

 except a small quantity of earthy matter, which con- 

 stitutes the ashes. In this way we make the first 

 division between the two distinct classes of the con- 

 stituents of plants. One portion escapes into the 

 atmosphere, and the other remains as a disorganized 

 earthy substance. 



That part which burns away during combustion 

 we will call atmospheric matter, because it was de- 

 rived by the plant from the air ; the ashes which re- 

 main we will call earthy matter, because they were 

 derived from the soil. The atmospheric matter has 

 become air, and it was originally obtained from air. 

 The earthy matter has become earth, and was ob- 

 tained from the soil. 



This is the first step toward a knowledge of agri- 

 cultural chemistry. The next will be to examine 

 each of these two different classes of matter, that we 

 may learn precisely of what they consist. Then we 

 must inquire where these substances are found, how 

 they are taken up by the plant, and how we can best 

 supply such as nature, unaided, does not always 

 furnish. This knowledge does not require that farm- 

 ers become chemists. All that is required is, that 

 they should know enough of chemistry to understand, 

 so far as the present state of knowledge makes it 

 possible, the nature of the materials of which their 

 crops are composed, and how those materials are to 

 be used to the best advantage. 



