ITS SOURCE, THE ATMOSPHERE. 23 



But it is inconceivable, that the functions of the 

 organs of a plant can cease for any one moment 

 during its life. The roots and other parts of it, 

 which possess the same power, absorb constantly 

 water and carbonic acid. This power is indepen- 

 dent of solar light. During the day, when the 

 plants are in the shade, and during the night, car- 

 bonic acid is accumulated in all parts of their 

 structure ; and the assimilation of the carbon and 

 the exhalation of oxygen commence from the instant 

 that the rays of the sun strike them. As soon as a 

 young plant breaks through the surface of the 

 ground, it begins to acquire colour from the top 

 downwards ; and the true formation of woody tissue 

 commences at the same time. 



The proper, constant, and inexhaustible sources 

 of oxygen gas are the tropics and warm climates, 

 where a sky, seldom clouded, permits the glowing 



of which we will suppose to be 1 05 square metres, and which receives 

 six coats of lime in fou* days, carbonic acid is abstracted from the air, 

 and the lime is consequently converted, on the surface, into a carbonate. 

 It has been accurately determined that one square decimetre receives in 

 this way, a coating of carbonate of lime which weighs 0.732 grammes. 

 Upon the 105 square metres already mentioned there must accordingly 

 be formed 7686 grains of carbonate of lime, which contain 4325.6 

 grains of carbonic acid. The weight of one cubic decimetre of carbonic 

 acid being calculated at two grammes, (more accurately 1.97978,) the 

 above mentioned surface must absorb in four days 2.163 cubic metres of 

 carbonic acid. 2500 square metres (one Hessian acre) would absorb, 

 under a similar treatment, 514 cubic metres zz 3296 cubic feet of car- 

 bonic acid in four days. In 200 days it would absorb 2575 cubic metres 

 164,800 cubic feet, which contain 10,300 Ibs. Hessian of carbonic acid 

 of which 2997 Ibs. are carbon, a quantity three times as great as that 

 which is assimilated by the leaves and roots growing upon the same 

 space. 



