118 THE CANADIAN NATURALIST. [April, 



The steps of research by which our present knowledge of this 

 matter was built up by Liebig, from data partly collected, partly 

 original, cannot be here enumerated, but the received view may be 

 thus briefly summed up : Every 32 lbs. of atmospheric oxygen 

 can take up, without change of volume, 12 lbs. of carbon in the 

 form of carbonic-acid gas. This gas, on the other hand, plants 

 have power to absorb by leaf and root ; and by their vital force, 

 coupled with the action of the solar light upon their leaves, to de- 

 compose. The carbon they reduce to the solid form, and fix in 

 their growing tissues ; the oxygen they restore to the air. The 

 oxygen thus liberated by living organisms takes up fresh carbon 

 from effete organic matter; whether from the debris of vegetables 

 themselves, e. g. mouldering humus, slowly oxydized within the 

 soil ; or from vegetal fuel (recent or fossilj rapidly oxydized by 

 combustion ; or from the residuary materials of animal life, circu- 

 lating in the blood, and eliminated by oxydation during the respi- 

 ratory process ; or lastly, from the final residuum of animal life, 

 — the corpse, which also, during its decay and dissolution, yields 

 carbon in abundance to the oxygen of the air. Thus, by the in- 

 tervention of atmospheric oxygen as its carrier, carbon, in the form 

 of carbonic-acid gas, is transferred from dead to living organisms, 

 the air constantly receiving from the former as much carbon as it 

 supplies to the latter. 



Cosmic Equilibrium of the Atmosphere, how far 

 DOUBTFUL. — Whether or not the ever-active processes which 

 collectively supply carbon to the air exactly balance those which 

 perpetually co-operate to withdraw it, so as to form a perfect and 

 unalterable cosmic equilibrium, we do not know. The assertion 

 is often made, and popular writers are in the habit of extolling the 

 assumed arrangement as an admirable provision of nature. But 

 we are in truth quite ignorant on this subject ; no reliable data 

 having come down to us as points of comparison by which to de- 

 termine any variation that may have taken place, and be still in 

 progress, in the composition of the atmosphere. And here the 

 Reporter cannot but remark in passing, that it is time systematic 

 observations were begun in Europe, to serve as a starting-point, 

 or first term of comparison, by which our successors, if not our- 

 selves, may be enabled to elucidate this question ; than which none 

 can be conceived of deeper importance to mankind. 



True Functions of Humus. — Reverting to the humus in 



