176 WHAT DOES MAN LIVE UPON? 



rain and by the lesser streams, to form what we know as 

 alluvium. 



Thus was the naked crust of our planet formed. But 

 formative processes, of which we neither have nor can have 

 any conception now, were in action from the very first ; 

 where the oceanic deposits lifted themselves, as transition 

 rocks, into the air, vegetable germs originated, which found 

 their sustenance in carbonic acid, ammonia and water, and 

 the products of the atmospheric corrosion of the rocks. A 

 world of organisms, teeming with life, originated on the 

 globe, the varied multiplicity of which was not dependant 

 on those four elements which, in a truer sense, form their 

 organic constituents, but rather on the infinite variety of 

 chemical processes which were called forth by the manifold 

 kinds and quantities of inorganic substances. On the 

 other hand, the humus, the black substance resulting 

 from the decay of living beings, rendered possible the 

 development of the innumerable organisms in greatest 

 force, since it furnished to them organic nutriment. But 

 the weathering of rocks, and their chemical decomposition 

 into soluble constituents, depend upon heat and the 

 chemical composition of the atmosphere. Conditions like 

 those which now we find only under the tropics, allow of 

 rapid weathering and rapid decomposition, and thus cause 

 the rich and luxuriant vegetation of the tropics. At a 

 former period, however, our atmosphere must have been 

 everywhere more moist, denser, and consequently warmer; 

 and in this age could unfold itself, without limit, over the 

 whole earth, that fulness of organic life which we now find 

 buried in a fossil condition in the stratified rocks, alto- 

 gether without relation to geographical latitudes. 



To return to my subject. The ingenious views esta- 

 blished by Licbig consequently point out, that those 



