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CHAPTER XL 



VEGETABLE SCAVENGERS. 



Drowned Fishes Burning and Breathing How Fire may be Extinguished 

 Carbonic Acid Gas: how produced, how disposed of ; taken up by 

 Leaves Quantity required by Beech Forest Oxygen returned to the 

 Air ; Seaweeds as Scavengers - Carbon in Vegetable Oils, Acids, 

 Sugars, Starch, Gums, Perfumes Other refuse Gases Fungi as 

 Scavengers Fermentation and Putrefaction Floating Matter of the 

 Air. 



WHEN Professor Nordenskjold was in the Arctic Ocean 

 he noticed that in one spot there were innumer- 

 able dead fishes. A shoal had evidently been entangled 

 among the ice, and becoming enclosed in a narrow space, 

 had been droivned ! 



" But how can fishes possibly be drowned ? " some one 

 may ask. Well, a man drowns for want of air, if his head be 

 kept under water, for drowning is practically the same thing 

 as suffocation ; and the fish, though it lives in water, needs 

 air as well as other animals, and being unable to decompose 

 the water, and so obtain oxygen, is dependent upon that 

 which is dissolved in the water. When that is exhausted it 

 must needs be suffocated. 



But why should not the same air be breathed over and 

 over again ? 



On one occasion M. Huber, having closed the entrance 

 of a bee-hive, noticed that, in a quarter of an hour, the bees 

 became uneasy, ceased working, and began vibrating their 



