STRUCTURE OF SOIL 



rest but a short time before they again set off on new 

 adventures. 



One might say the same of the water, and of the carbonic 

 acid gas and oxygen of the atmosphere, for the water, falling 

 as rain upon the earth, trickles down to the underground 

 water-level. Then it immediately begins to rise up be- 

 tween the particles of earth and is promptly caught and 

 sucked in by the roots, only to be again given out by their 

 leaves. The carbonic acid gas and oxygen also are always 

 entering and leaving the foliage. Even the nitrogen of the 

 air is not left alone in the atmosphere. There are small 

 germs in the soil which are able to get hold of it and make 

 it into valuable nitrates. 



More curious still is the fact that electric charges can be 

 used to change the comparatively useless air-nitrogen into 

 useful manures. Probably the farmer will some day make 

 his own nitrates by electricity. 



The structure of the soil or earth is a most interesting 

 and romantic part of botany. It is true that a "radical'' 

 disposition is necessary if one is to go to the root of the 

 matter, but, unless we do this, it is impossible to realize the 

 romance of roots. 



Down below is the unaltered rock, sand, or clay. Next 

 above it comes the subsoil, which consists of fragments of 

 the rock below, or of sand, clay, etc., more or less altered by 

 deep-going foots. Even in this subsoil, bacteria or germs 

 may be at work, and the burrows of worms and insects often 

 extend to it. Next above the subsoil comes the true soil ; 

 there is plenty of the stones, soil, sand, or whatever it may 

 be that constitutes the subsoil, but its richness consists in 

 its contents of valuable minerals, and especially of broken- 

 up leaves, corpses of insects, and manure. Above this true 



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