26 THE FIRST BOOK OF FARMING 



the relative amounts of sand and clay in the soil. 

 Also if we weigh a sample before and after burn- 

 ing we can tell roughly the amount of organic mat- 

 ter in the soil. Test a number of soils and deter- 

 mine roughly the proportions of sand, clay and 

 organic matter in them. 



Experiment. Take the pans of soil used in our 

 first soil experiment and separate the soils in the 

 pans into two parts by a trench across the centre 

 on the pan. Now wet the soil in one side of the 

 pan and stir it with a stick or a spoon, carefully 

 smooth the surface of the soil in the other side of 

 the pan and pour or sprinkle some water on it, but 

 do not stir it. Set the pans aside till the soils are 

 dry. This drying may take several days and in the 

 meantime we will study the classification of soils. 



CLASSIFICATION OF SOILS 



Soil materials and soils are classified as follows : 



Stones. Coarse, irregular or rounded rock frag- 

 ments or pieces of rock. 



Gravel. Coarse fragments and pebbles ranging 

 in size from several inches in diameter down to 

 1/25 inch. 



Sand. Soil particles ranging from 1/25 of an 

 inch down to 1/500 of an inch in diameter. Sand 

 is divided into several grades or sizes. 



Coarse sand 1/25 to 1/50 of an inch. 

 Medium sand 1/50 to i/ioo of an inch. 



