1896.] on the Circulation of Organic Matter, 159 



oxygen by the animal. If among the herbage there be plants of 

 clover, it is now certain that much of the atmospheric nitrogen will 

 be drawn into the soil to nourish these plants and generally to increase 

 its fertility. Whether the return of oxygen, carbon and nitrogen is, 

 in the long run, equal to the intake we cannot tell. 



When, however, we ponder upon the gradual increase of vegetable 

 soil or humus with which the bare rocks have been clothed in the 

 course of ages, it is almost impossible not to come to the conclusion 

 that the humus and with it the fertility of the soil has steadily in- 

 creased at the expense of the sea on the one hand, and, possibly, 

 of the atmosphere on the other. To put the matter in the form of 

 question and in other terms, " Does the Lithosphere increase at the 

 expense of the Atmosphere and the Hydrosphere ? " Does the land 

 increase at the expense of sea and air ? Be this as it may, it seems 

 certain that by scrupulous return to the soil of all that comes out of 

 it the resources of nature are made increasingly available for tho 

 benefit of man. 



When organic matter is mixed with water, a process of putrefac- 

 tion and fermentation is started, and the organic matter, instead of 

 undergoing oxidation, is reduced, and among the commoner products 

 ■of this process are ammonia with sulphuretted hydrogen and marsh- 

 gas, which are both combustible. These processes furnish us with 

 other combustible matters among the commonest of which are the 

 alcohols, the familiar products of fermentation. 



It is interesting to note the tendency of organic matter, when 

 mixed with water, to give rise to explosive and combustible products. 

 Explosions in cesspools and sewers have occurred many times. 

 When wet hay is stored in stack it catches fire. When we stir the 

 mud at the bottom of a pond or river, bubbles of combustible marsh= 

 gas rise to the surface. The coal measures are due to the storing 

 under water of semi-aquatic plants which have been preserved by 

 being silted up, and we know that coal is full of defiant gas, marsh- 

 gas, sulphuretted hydrogen and carbon monoxide, which are all com- 

 bustible, and that the carbonaceous residue, charged with volatile 

 and combustible hydro-carbons, forms the chief fuel of the civilised 

 world. Peat is formed in ways analogous to that of coal, and the 

 so called mineral oils are certainly the products of organic matter 

 which has been silted up. 



These subterranean stores of combustibles, all of organic origin, 

 are, as we know, prodigious in quantity. Nobody can predict the time 

 which it will take to exhaust the coal measures of the world, and we 

 know for a fact that the sacred fires of Baku on the Caspian, fed by 

 subterranean reservoirs of naphtha, have been burning for centuries. 



When we see the end of a tin of " preserved meat " bulged, we 

 know that the gas-forming organisms have been at work within, and 

 when the bed of the lower reaches of the Mississippi rises as a small 

 mud mountain, spluttering with carburetted hydrogen, we know 



