THE AGE OP THE EAETH. 85 



Avater flowing direct out of tlie eartli at Banif (Canada),* lives 

 without help from any ingredients of the atmosphere above it, 

 and takes from the water and from carbonic acid or carbonates, 

 dissolved in it, the hydrogen and carbon needed for its own 

 growth by the dynamical power of smdight; thus leaving free 

 oxygen in the Avater to pass ultimately into the air. Similar 

 vegetation is found abundantly on the terra,ces of the Mam- 

 moth hot springs and on the beds of the hot water streams 

 flowing from the Geysers in the Yellowstone National Park 

 of the United States. This vegetation, consisting of confervas, 

 all grows under flowing water at various temperatures, some 

 said to be as high as 74° Cent. We cannot doubt but that 

 some such confervaB, if sown or planted in a rivulet or pool 

 of warm "water in the early years of the first century of the 

 solid earth's history, and if favoured with sunlight, would 

 have lived, and grown, and multiplied, and w^ould have 

 made a beginning of oxygen in the air, if there had been 

 none of it before their contributions. Before the end of the 

 century, if sun-heat, and sunlight, and rainfall, were suitable, 

 the whole earth not under water must have been fitted for 

 all kinds of land plants Avhich do not require much or any 

 oxygen in the air, and which can find, or make, place and 

 soil for their roots on the rocks on which they grow ; and 

 the lakes or oceans formed by that time must have been 

 quite fitted for the life of many or all of the species of 

 water plants living on the eartli at the present time. The 

 moderate Avarming, both of land and Avater, by underground 

 heat, toAvards the end of the century, would probably be 

 faA'Ourable rather than adA'crse to vegetation, and there can 

 be no doubt but that if abundance of seeds of all species of 

 the present day had been scattered over the earth at that 

 time, an important proportion of them would have liA'ed and 

 multiplied by natural selection of the places where they 

 could best thriA^e. 



§ 42. But if there was no free oxygen in the primitive 

 atmosphere or primitiA'e Avater, seA^eral thousands, possibly 

 hundreds of thousands, of years must pass before oxygen 

 enough for supporting animal life, as we now know it, was 

 produced. Even if the average activity of vegetable 

 groAvth on land and in water oA-er the Avhole earth AA'-as, 

 in those early times, as great in respect to evolution of 



* Eocky Mountains Park of Canada, on the Canadian Pacific 

 EailwaA-. 



