150 PRODUCES CARBONIC j^CID AND WATER. 



It will be recollected (p. 135) that in forming an equivalent of woody 

 iibre or of sugar, 24 of oxygen were given off, chiefly by the leaf — so in 

 again resolving these substances into carbonic acid and water, 24 of oxy 

 gen, are absorbed. Thus — 



1 of Woody Fibre = Ci2 Hs Og 

 24 of Oxygen . = O24 



12 of 8 of 



Carbonic Acid. Water. 



Sum. . . =:Ci2H3 O30 = 12CP2 -f 8HO. 



Or, 1 of Cane Sugar =Ci2HioOi„ 

 24 of Oxygen . . = O-,. 



12 of 10 of 



Carbonic Acid. Water. 



Sum. . . =Ci2 Hio O34 =12CO2 + 10HO. 



The same law holds in regard to all other vegetable substances. They 

 are resolved into carbonic acid and water, in proportions which neces- 

 sarily vary with the chemical constitution of each. 



It applies also to all bodies of vegetable origin, among which nearly 

 all combustible minerals may be reckoned. The peat and coal we burn 

 in our houses and manufactories, when supplied with a sufficiency of 

 atmospheric air, are resolved during combustion into carbonic acid and 

 watery vapour. 



Some vegetable substances contain a small quantity of nitrogen. 

 "When these are burned, this nitrogen escapes into the atmosphere, — 

 generally in an uncombined state, — and mingles with the air. So in 

 animal substances, nearly all of which contain nitrogen as an essential 

 constituent. During perfect combustion the whole of the carbon is dis- 

 sipated in the form of carbonic acid, while the nitrogen rises along with 

 it in an elementary state- 



The result of this uniform subjection of all combustible matter to the 

 operation of this one law, is the constant production on the surface of 

 the globe of a vast quantity of carbonic acid ; — the re-conversion of large 

 masses of organic matter info the more elementary compounds from 

 which it was originally formed. 



How interesting it is to contemplate the relations, at once wise and 

 beautiful, by which through the operation of such laws, dead organic 

 matter, intelligent man, and living plants, are all bound together ! The 

 dead tree and the fossile coal lie almost useless things in reference to 

 animal and vegetable life, — man employs them in a thousand ways as 

 ministers to his wants, his comforts, or his dominion over nature — and 

 in so doing, himself directly though unconsciously ministers to the wants 

 of those vegetable races, which seem but to live and grow for his use and 

 sustenance. 



It is impossible to say what proportion of the carbon absorbed during 

 the general vegetation of the globe, is thus annually restored to the at- 

 mosphere by the burning of vegetable matter. That it must be very 

 great, will appear from the single fact, that by far the greater part of the 

 globe is dependent for its supply of fuel on the annual produce of its 

 forests; — while even in those more favoured countries where mineral 

 coal abounds, the quantity of wood consumed by burning falls but little 

 short of the entire yearly growth of the land. 



