38o 



NATURE STUDY AND LIFE 



wood, leaves, and all kinds of vegetable matters burn 

 up readily ; and we know that coal is vegetable matter 

 that has been buried in the earth. We must be sure 



that the samples 

 are dry before 

 we weigh them ; 

 then we will 

 see how much 

 of them we can 

 burn away. To 

 do this we will 

 place the sample 

 on a clean piece 

 of tin or sheet 

 iron and heat it 

 red hot over a 

 gas stove or over 

 a bed of coals in 

 the furnace, and, 

 after we are sure 

 no more can be 

 burned away, 

 we will weigh 

 again. We saw 

 that the lea'f 

 mould burned 

 brightly and left 

 a light mass of ashes on the tin. These weighed 22 grams, 

 which means that leaf mould is 78 per cent vegetable 

 matter. The black loam from the woods left more earth 

 and ashes behind. This remainder weighed 89 grams, 



Fig. 152. How a Chestnut Tree holds Soil 



TOGETHER 



