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THE BOOK OF NATURE STUDY 



the others. The scheme of the experiment is best summarised 

 in a table. 



Place the flasks aside in a warm dark cupboard and examine 

 those containing sugar after a week or ten days has elapsed. The 

 liquid in the flask without carbonate of lime will be all covered 

 with moulds, mostly white in colour, but others that are green 

 and black and even pink may also be in evidence. The contents 

 of the flask containing carbonate of lime will show a very different 

 growth, probably a dirty skin much blown with bubbles of gas. 

 Replace this flask in the cupboard for examination in two or three 

 months' time. The soil introduced has evidently started very 

 considerable actions, which are further of an entirely different 

 type according as carbonate of lime had been added or not. 

 The soil, in fact, contains a great variety of organisms, some of 

 which flourish best in a slightly acid medium, while others can 

 only develop where it is kept neutral. That it is the living 

 soil which starts these changes is seen from the absence of action 

 in the check flask which had been heated after the addition of 

 the soil. 



The other three flasks should be left for a month, and then a 

 little of the clear liquid in each must be evaporated in a basin 

 and tested with di-phenylamine for nitrates. Here again there 

 will be no evidence of action in the flask which has been heated 

 after the addition of the soil, and of the other two, inoculated 

 with living soil, only the one containing carbonate of lime will 



