252 



♦ KNOW^LEDGE ♦ 



[September 1, 1888. 



nence in the solid crust formed in various parts of the earth 

 iu this stage of her career. Immense tracts of liquid surface 

 would solidify through some relatively slight chacges of tem- 

 perature or other conditions ; hut the crust thus formed would 

 be fissured from time to time by the seething liquid masses 

 beneath ; and often large regions of fiery hot crust would be 

 converted suddenly into the liquid condition through the 

 action of currents of hotter matter rising underneath them. 

 Or, as large fields of ice are carried now by ocejxnic currents 

 into regions where they are melted by the warmer waters 

 around them, so in those eai-lier days of the earth would 

 immense ti-acts of glowing crust be carried to regions where 

 they would melt in the fervour of the hotter liquid beneath 

 them, and resume the liquid condition out of which they had 

 for a time passed. 



Among the substances now mostly liquid which must 

 have been almost wholly vaporous throughout the second 

 stage of the eai-th's orb-life, water of course must be regarded 

 as the most important. Water could not have rested, in 

 the liquid state, on the intensely hot surface of our earth in 

 this part of her life. It is true that the atmosphere must 

 have been far more dense then than now, because it must 

 have included immense quantities of gaseous and vaporous 

 matter not now present in it except in very small amount : 

 and under such an atmosphere water might be heated till it 

 shone with its own inherent light, without being converted 

 into steam. But the temperature of the crust must have 

 been greater even than this would imply. And though a 

 few lakes and pools of red hot water may have gathered 

 from time to time on the ever moving white hot crust of the 

 earth, yet far the larger portion of the water must have 

 lieen vaporised, forming a vast atmosphere of steam, which 

 close by the earth's glowing surface would be self-luminous. 

 At considerable heights above that surface the steam would 

 condense in the form of visible clouds, not .self-luminous, but 

 lit up on their inner side by the fiery surface of the 

 crust beneath. Probably seveial layers of clouds would 

 form at different heights. The lowermost layer would give 

 off vapour from its upper side, to rise to a greatei- height, 

 and form by fresh condensation another layer, only illu- 

 minated by such liglit from the crust as passed between the 

 clouds of the lowest layer. And the process would pro- 

 bably be repeated in such sort that several layers would be 

 formed enclosing the earth's real globe at different distances 

 from its glowing surface. What the depth of the complex 

 atmosphere of the earth in that stage of her career may have 

 been, it is not easy to determine. For what we know of the 

 sun and (less certainly but still clearly enough) of the giant 

 planets, shows that the laws of the gaseous pressure and 

 density prevailing within such limits as bound the experi- 

 ments of our physicists, do not hold at the high temperatures 

 and tx-emendous pressures existing certainly in the sun and 

 giant planets, and almost as certainly in our earth's dense atmo- 

 sphere when she was in the first two stages of her planet life. 

 To show that this is so, it is only necessary to note that, 

 whereas terrestrial experiments have taught that there is a 

 critical temperature for each gas, at higher temperature than 

 which no amount of pres.sure will produce liquefaction, were 

 this true of the sun, not only would every particle of his 

 substance be vaporous, but density increasing with pressure 

 in gases and vapours (except where liquefaction is ap|iroach- 

 ing, which is not here the case), the compression would be .so 

 great even a few thousand miles below the visible limits of 

 his atmosphere that the density even of hydrogen would be 

 greater many times than that of platinum, the heaviest 

 element known on earth. We not only know that this is 

 impos.sible, but that the mean density of the sun, insteiid of 

 being thus enormous, is only about a fourth of the mean 

 density of the earth. We can infer from this that under 



the conditions existing when our earth was in the sun- like 

 and fiery stages of her career, an atmosphereof great extent, 

 with probably many successive layers of cloud, surrounded 

 her fiery globe, whose partly liquid partly solid surface, 

 though glowing with a white heat, probably could pour no 

 portion of its light thi'ough the enwrapping cloud-masses. 



We may also confidently infer that in the earth's deep 

 atmosphere in this earlier stage of her life, vertical move- 

 ments of great energy took place, as immense volumes of 

 compressed vapours (not steam alone) were flung upwards 

 with tremendous energy in volcanic explosions, or as cloud 

 masses in which whole seas of water were contained gave 

 birth to cataracts (rather than torrents) of intensely hot 

 water, stronglj- charged with destructive acids. We may 

 have to look to other planets for evidence that such vertical 

 displacements do actually take place during the earlier stages 

 of world life. Yet,- reasoning on what our earth's condition 

 must have been at such stages in her life, or on what it 

 would now be if she were placed as in some vast crucible 

 and heated throughout her whole frame till her crust shone 

 white again, we see that vertical movements of both kinds, 

 eruptional or upwards and torrential or downwards, cannot 

 but have been constantly in progress throughout her deep, 

 complex, and cloud-laden atmosphere. Such movements, by 

 altering the distance of the moving masses from the axis of 

 rotation, would cause either a lagging or a relative advance 

 of these masses amongst those into which they were ascend- 

 ing or descending respectively — in other words, bands or 

 zones of vaporous or cloudlike nature, akin to the zones of 

 Jupiter and Saturn, foinied in the deep and complex 

 atmosphere of the earth at that stage of her orb-life. 



After millions more of years the earth became ready to 

 enter on that part of her existence which may be called her 

 life-bearing career. Not everywhere on her surface at once, 

 but in certain regions — possibly the polar portions — where 

 the cooling was first suflicient, certain lower forms of life, 

 scarcely distinguishable then as vegetable and animal, wovild 

 lie possible. Appaiently the conditions which rendered 

 them possible were also such as to bring about their genera- 

 tion — we know not how, and still le.ss do we know why. 

 ^Multitudinous germs of life, not necessarilj' multitudinous 

 in form, possibly including but a few forms, possibly but a 

 single form, must have appeared on the earth iu a very 

 early portion of the present stage of her life — millions of 

 years probably liefoi-e the era to which geologists attribute 

 the Archaean or most ancient rocks of the earth (preceding 

 those called primary by geologists), for from such germs 

 alone could the forms of life which we recogni.se in the 

 fossils of the lowest of the primary rocks have been 

 develojjed. So much we are assiired of; but as to the 

 manner in which such germs of life came into existence, 

 and the way in which the property we call vitalit)' came to 

 belong to them, we know no more than we do of the manner 

 in which the materials of which suns and planets have been 

 formed came first to be, or of the way in which those 

 materials came to have the specific properties which we 

 know they possess. 



It is not even from the stage thus reached, remote in the 

 past as it must be, that we can trace the earth's record. 

 Millions of years must have passed before the simple 

 primordial forms of life, animal and vegetable, had developed 

 (along certain lines) into the specialised and often highly 

 complex forms found in the lowest of the geological strata. 

 Of the interval we have scarcely even any records in the 

 material changes which took place as the Arch;ean rocks 

 were forming. It is scai-celj' to lie hoped that any traces ot 

 life of that ante-piimary era will ever be discovered, so un- 

 favourable were all the conditions for the preservation ot 

 animal or vegetable remains. 



