morraine-like deposits by far-extending glaciers, existing and flowing during 

 what is generally spoken of by geologists as the glacial or as the drift 

 period, a period long anterior to the 6000 years which constitute what we 

 may designate the historical era of the world's existence ; and to deposits on 

 a stupendous scale of what were the lits de dejection of torrents — compared 

 with which the torrents of the present day are as tiny streamlets — the 

 regime of which followed close upon the glacial era, succeeding it apparently 

 immediately, and giving occasion for the designation the torrential era, 

 intermediate, there at least, between the eras of glacial and of alluvial 

 deposits. 



M. Costa advances similar views in regard to the character of the 

 geological formation upon which M. Cezanne founds his theory, but he 

 considers that the morraine-like deposits, which ^I. C6zanne attributes to 

 glacial action, may have been, and probably were, like the others, the litg 

 de dejection of torrents, and he alleges that, compared with the regime of 

 torrents, the regime of glaciers is temporary, local, and accidental ; while 

 this is imiversal, extending to aU lands, if not also to aU worlds, and 

 extending over all time. 



We are thus by both carried back to a time in which, if the earth was 

 not without form and void, the mountains then were naked and bare. 



Observation shows that, now at least, soil capable of nourishing plants 

 when exposed naked and bare is soon covered with vegetation. A httle 

 decaying cheese, or firuit, or damp bread, so exposed is soon covered with 

 mould. In experiments designed to test the hypothesis of spontaneous 

 generation, ingenuity seems to be baffled in the endeavour to devise a 

 crucial experiment which shall either establish or disprove the hypothesis. 

 Under conditions the most unlikely, the simpler organisms make their 

 appearance ; to prevent this has hitherto proved impracticable, if it be 

 not impossible ; and what is seen thus in the laboratory on a simple scale is 

 seen on a large scale taking place everywhere. 



" Whenever a tract of country, once inhabited and cultivated by man," 

 says Marsh, "is abandoned by him and by domestic animals, and 

 surrendered to the undisturbed influences of spontaneous nature, its soil 

 sooner or later clothes itself with herbaceous and arborescent plants, and, 

 at no long interval, with a dense forest growth. Indeed, upon surfaces of 

 certain stability ■ and not absolutely precipitous inclination, the special 

 conditions required for the spontaneous propagation of trees may all be 

 negatively expressed and reduced to these three : exemption from defect or 

 excess of moisture, from perpetual frost, and from the depredations of man 

 and browsing quadrupeds. Where these requisites are secured, the hardest 

 rock is as certain to be overgrown with wood as the most fertile plain, 

 though, for obvious reasons, the process is slower in the former than in the 

 latter case. Lichens and mosses first prepare the way for a more highly 

 organised vegetation. They retain the moisture of rains and dews, and 

 bring it to act, in combination with the gases evolved by their organic 

 processes, in decomposing the surface of the rocks they cover ; they arrest 

 and confine the dust which the wind scatters over them, and their final 

 decay adds new material to the soil already half-formed beneath and upon 

 them. A very thin stratum of mould is sufficient for the germination of 

 seeds of the hardy evergreens and birches, the roots of which are often 

 found in immediate contact with the rock, supplying their trees with 

 nourishment from a soil deepened and enriched by the decomposition of 



