46 
of water, namely, oxygen and hydrogen. In the ash we should 
find oxide of iron, lime, magnesia, potash, soda, phosphoric acid, 
sulphuric acid, chlorine, and silica. These various substances 
would on the average be present somewhat in the proportions set 
down as follows :— 
AVERAGE COMPOSITION OF PLANTS. 
Parts in 
100,000, 
Matter dissipated on drying, consisting almost wholly 
of water 60 sai Pee wey ... 72,000 
Matter dissipated on burning, consisting of— 
Carbon... ste ee ... 11,000 
Nitrogen ..- die yp ace 750 
Elements of water (oxygen and hydrogen) 14,250 
26,000 
Matter left behind after burning (ash), consist- 
ing of— 
Oxide of iron iis ies aie 20 
Lime an ae a aie 300 
Magnesia ... sa oo ase 125 
Potash... sé a oS 550 
Soda aes ore on sain 70 
Phosphoric acid —... i fer 270 
Sulphuric acid iss #66 site 80 
Chlorine ... des si ang 85 
Silica ae cir eae 500 
— 2,000 
100,000 
Now, where does a plant obtain these different substances, 
where can it find the food with which to supply them? Are they 
obtainable from the soil? Let us see what the soil contains. 
Were we to put a sample of soil through the same process of 
rough analysis as we did the plant, namely, by drying and then 
burning it, we should get similar results; it would give off steam, 
