CHAPTER X 



HOW THE CHEMIST WENT FARMING 



Sir Daniel Hall and his Experiments 



A POET has spoken of " dead earth." Take up a 

 handful of soil from your garden and examine it. 

 You are holding a very large number of particles 

 of rock broken up by frost and rain, and mixed with a 

 certain amount of decayed or decaying animal and 

 vegetable matter. Apparently it is all dead enough, yet 

 put a pinch of that soil under a powerful lens and you 

 will see millions of living creatures, which multiply with 

 immense speed. These are bacteria, and the top layers of 

 the soil are full of them. Three or four feet down, how- 

 ever, they almost cease to exist, and below a certain depth 

 the soil is dead indeed. 



Without these tiny atoms of restless life no plant could 

 grow. Although they are invisible to the naked eye, they 

 are precious beyond gold, for without them our planet's 

 surface would be as dead as that of our satellite the moon. 



But plants, you say, do not live on bacteria. That is 

 so, yet certainly they cannot live without them. Put a 

 cartload of stable manure on your garden in the spring, 

 and how much of it is visible when you do your next 

 winter's digging? Practically none, and you say the 

 plants have used it. 



But a plant cannot eat manure. It can only feed upon 

 it after it has been converted into something else. The 

 agents for that conversion are the tiny living creatures 

 named bacteria. They are almost incredibly small. Most 

 of them average between one twenty-five-thousandth 

 and one fifty-thousandth of an inch in diameter, 



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