No. 144.] 497 



Now, if the action of the sun and the chemical condition of the 

 air are unvarying circumstances in the life of a plant — if all our 

 endeavors to increase its growth must be directed to the roots, it 

 becomes of interest to enquire into the services of carbonic acid. 

 These are two, absorption and decay. 



1. Absorption. — Charcoal absorbs many times its own volume 

 of this gas, and gives it out again to the growing rootlets of plants, 

 and it is to this action, rather than to any salts that it may con- 

 tain, that its well known stimulating action on growing vegeta- 

 bles is to be attributed. Once in the charred condition, woody 

 matter seems to be permanent in all conditions of air, and moist- 

 ure. -KmiMS or decayed wood, however, exerts nearly the same 

 absorbing power, and by a continuation of the decay also gene- 

 rates the acid gas that it absorbs. But it is to the moisture con- 

 tained in the soil that absorption from air is principally due. 



2. B^cay. — This is the great source from which carbonic acid, 

 the principal food of plaiits, is derived, and one of the most im- 

 portant indications in the agricultural treatment of the soil, is to 

 •ensure the destruction of the agricultural portion of it. When 

 wood is buried below a few inches, its decay goes on very slowly. 

 Fence posts rot first at the surface of the earth. Those portions 

 that lie a foot or so deep remaining sound. 



Woody fibre, buried beyond the action of the air or protected 

 from the air by being completely immersed in water, is preserved 

 by its seclusion. Hence the great fertility of drained marshes, 

 and the increased fertility of underdrained fields, and the policy 

 of subsoiling by which the under stratum is stirred, while the 

 organic substances are not buried beyond the influence of the air. 

 To wliat extent manure should be covered to ensure the absorp- 

 tion of its gaseous constituents, has always been an open question. 

 Where its fullest effects are desired on the first crop, it should be 

 buried no deeper than just in this way to save it all. The esca- 

 ping odor tells the necessity of covering ammoniacal manures, and 

 carbonic acid is, I believe, not quite as readily absorbed. 



Granite, "and the rock may with propriety be said to have the, rot, for it crumbles topieces in 

 the hand. The Phenomenon, may, without doubt, be ascribed to the continued disengage- 

 ment of carbonic acid gas from numerous fissures."— [Lyell's Prin. Geo., vol. 1, p. 317.] 



[Assembly, No. 144.J F 2 



