THE CONTENTS OP THE SOIL 



29 



25c. The organic matter in soils the plant and animal 

 remains is removed by burning. Let the pupil secure a cupful 

 of wet soil and carefully weigh it on delicate scales. Then let 

 it dry in the sun, and weigh again ; the difference in weight is 



T 



Fig. 1. Showing the wearing away of mountain peaks anil the formation of 

 soil at the base. 



due to the loss or evaporation of water. Now place it in a 

 moderately warm oven or on a stove, and after a few minutes 

 weigh again ; more of the water will now have passed off. Now 

 thoroughly burn or bake it, and weigh ; the loss is now mostly 

 due to the burning of the organic matter, and part of this 

 matter has passed off as gas. If there is no perceptible loss 

 from the burning, it is evidence that the sample contained little 

 organic matter. Note the difference in results between clay and 

 muck. The pupil may also be interested to try to grow plants 

 in the baked soil. 



