AND AGRICULTURE. 35 



Then take a dry glass tube, from ten to twenty 

 inches long, and about one inch in diameter, and 

 pass it over the jet, as in the cut. A musical 

 sound will be heard issuing from the tube, which 

 will soon become moist on the inside. If a tube 

 is not to be had, a dry tumbler may be used, 

 and the water produced will be condensed inside 

 it. Now, whence came the water ? The hydro- 

 gen gas, in burning, united with just sufficient 

 of the oxygen contained in the air to make water. 

 Gluten, unlike the substances already de- 

 scribed, contains four elements ; it contains nitro- 

 gen, in addition to carbon, hydrogen and oxygen. 

 The nitrogen which plants require, to make glu- 

 ten, is obtained almost wholly from the soil. 



OF THE SUBSTANCES WHICH FORM SOIL. 



The soil contains two kinds of matter, organic, 

 or the part which is combustible ; and inorganic, 

 or the part which will not burn. 



This may be shown by heating a small portion 



Questions. Where does the hydrogen, in burning, get the 

 oxygen necessary to make water ? How many elements does 

 gluten contain ? Name them. Whence do plants obtain 

 their nitrogen ? How many kinds of matter are there in 

 soil ? Name them. 



