THE SOIL 



29 



kept yourself warm by exercise, you became chilled. This was 

 because the heat which would have kept your body comfortable 

 was being used to evaporate the water from your clothes. 



EXPERIMENTS 



1. Take three boxes of the same size and fill one with dry sand, one 

 with dry clay, and one with dry loam. In each insert a thermometer to 

 a depth of two inches. Take the temperature at 9 A.M. Set the boxes 

 in the sunshine and take the temperature at 12 M. Put in the shade 

 and take the temperature at 4 P.M. What differences do you notice? 



2. Put a cupful of dry sand, one of wet sand, and one of water on 

 a warm stove. Which becomes warm first and which last ? Why ? 



3. Take the temperature at midday of the soil two inches below 

 the surface in a wet, undrained field and in a well-drained field. What 

 difference do you find ? Explain the reason. 



COMPOSITION OF THE SOIL 



Elements. We are apt to think of the objects around us as 

 simple substances, but this is seldom the case. Plants, animals, 

 the soil, and even most rocks are made up of several elements, 

 or simple substances. These are mixed and combined in different 

 ways so as to produce very different results. Strange as it seems, 

 it is none the less true, that our bodies, a blade of grass, and the dust 

 under our feet are composed of almost the same elements. Chem- 

 ists have proved this by separating these compound substances into 

 the simple ones composing them. As the farmer measures wheat 

 and the grocer weighs flour, so the chemist measures and weighs 

 the elements of the soil, air, and water, of plant and animal bodies. 



Elements as Plant Food. Although we may never wish to 

 separate and examine them as does the chemist, it is well for us to 

 know something about these elements. We are interested in the 



