G. E. Wieland — Polar Climate in Time. 407 



Paleozoic, though subject throughout, let it be repeated, to the 

 shuttle of seasonal change due to orbital eccentricity. But 

 let us now turn to the biologic record. 



Theoretical early polar life^ and the generalized conditions 

 of the Paleozoic. — If it were permissible to accept the sug- 

 gestion made by Chamberlain"^ and others that the early his- 

 tory of the globe was mainly one of quiet meteoric aggrega- 

 tion without the fusion of all its mass at any time, the period 

 during which the origin, or introduction, of life could hav^e 

 taken place might be considered as greatly lengthened, and 

 extending back into very novel conditions. But although this 

 idea may have very important elements of truth in it, it is one 

 requiring much further elaboration, and as we shall see need 

 not here be taken up. The hypothesis of the early nebular 

 constitution of the solar system and of the molten globe, as 

 formulated by Kant and by Laplace, and as supported by most 

 of the every-day facts of geology, astronomy, physics, and 

 chemistry, as well as rigid mathematical interpretation, must as 

 yet afford the main basis of speculation. One cannot but 

 admire the confidence with which Lord Kelvin speaks of the 

 first formed crust of the molten globe a few centimeters thick, 

 and says that, " All the reckonings of the history of the under- 

 ground heat .... are founded on the very sure assumption 

 that the material of our present very solid earth all round its 

 surface was at one time a white-hot liquid." 



Now in the face of concrete facts, bare suggestions to the 

 contrary cannot have a very great weight. If the molten 

 globe is to be accepted as a reality, it is then clear that perhaps 

 in part owing to the equatorial bulge, but mainly because 

 heavy tides and currents must long have continued to break up 

 the initially formed crust in the equatorial regions, there must 

 first have appeared at the poles suflQcient crustal stability to 

 make hot water life possible. It is also to be recalled that as 

 strongly indicated by G. H. Darwin's hypothesis, the moon 

 must have been at this early period much closer to the globe 

 than now. If so there must long have been produced lunar 

 tides of tremendous power sufficient to break up crusts of 

 many meters in thickness in the equatorial regions, while at 

 the pole weak tides would rule. A great interval of time 

 must then have elapsed between the first appearance of crustal 

 stability at the poles and at the equator, an interval of time 

 enough for the formation all round an undisturbed molten 

 globe of a crust a sufficient number of meters in thickness to 

 resist the lunar and solar tidal stress. This length of time 

 between the appearance of stable conditions suitable to the 



* On Lord Kelvin's address on the Age of the Earth as an abode fitted for 

 life. Annual Report Smithsonian Institution, 1899. 



