carbonic acid of the primeval atmosphere is being restored 

 to that condition by artificial means, in the present day,) we 

 must be convinced that this is an important item amongst 

 the causes which remove oxygen from the air, and substitute 

 carbonic acid. Besides this there are many processes con- 

 stantly being carried on in the laboratory of nature, which 

 produce one or other of these effects upon the atmosphere. 

 Amongst those which are constantly introducing large volumes 

 of carbonic acid, we may mention the active volcanos of the 

 old and new world, more especially the latter. Amongst 

 those causes by which oxygen is removed, we may mention 

 the constant action of dead matters upon the oxygen of the 

 air, this gas entering into combination with their elements. 

 It is thus that metals rust, that rocks and buildings moulder 

 away, that dead animal and vegetable substances decompose 

 and putrefy, and that change and decay gradually invade 

 all material substances, even the most durable. These are 

 effects which we popularly attribute to time ; but there is no 

 necessary connection between the lapse of ages and the decay 

 of material existences ; this is due to the action of oxygen, 

 and to other chemical and physical agencies constantly at 

 work, but which, working slowly, require time to display 

 their results; and if these were arrested, time would pass 

 by innocuous. Or, to resume the metaphor, these are the 

 scythe of time, armed with which his power is irresistible; 

 but which taken out of his hands would be inoperative, and 

 deprived of which he himself would become harmless. 



It is no improbable conclusion, as we conceive, that all 

 these agencies which we have enumerated, acting similarly 

 upon the atmosphere, would (were they unopposed) produce 

 in it an appreciable deterioration,* within a comparatively 



* Were any change produced in the atmosphere by these causes, it would be 

 permanent and constantly increasing; and though, for a short time, such a 

 change might not be injurious to the health of animals, yet in the course of 



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