AGE OF THE EARTH AS AN ABODE FITTED FOR LIFE. 355 



41. It is, however, possible, althougli it might seem not probable, that 

 there was free oxygen in the iDrimitive atmosphere. With or without 

 free oxygen, however, but with sunlight, we may regard the earth as 

 fitted for vegetable life as now known in some species, wherever water 

 moistened the newly solidified rocky crust cooled down below the tem- 

 perature of 80° or 70° of our present Centigrade thermometric scale, a 

 year or two after solidification of the primitive lava had come up to the 

 surface. The thick, tough velvety coating of living vegetable matter 

 covering the rocky slopes under hot water flowing direct out of the 

 earth at Banff (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 sunlight; thus leaving free 

 oxygen in the water to pass ultimately into the air. Similar vegetation 

 is found abundantly on the terraces of the Mammoth 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, con- 

 sisting of confervie, all grows under flowing water at various tempera- 

 tures, some said to be as high as 74° C. We can not doubt but that 

 some such confervjc, 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 favored with sunlight would have lived, and grown, and multi- 

 plied, and would 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 

 which 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 

 earth at the present time. The moderate warming, both of land and 

 water, by underground heat, toward the end of the century, would 

 probably be favorable rather than adverse 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 pro- 

 portion of them would have lived and multiplied by natural selection 

 of the places where they could best thrive. 



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

 primitive water several 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 veg- 

 etable growth on land and in water over the whole earth was, in those 

 early times, as great in respect to evolution of oxygen as that of a 

 Hessian forest, as estimated by Liebig'-^ fifty years ago, or of a culti- 



'Rocky Mountains Park of Canada, on the Canadian Pacific Railway. 

 ^Liebig: "Chemistry in its application to Agriculture and Physiology," English, 

 second edition, edited by Playfair, 1842, 



