CHAP. IX.] 



MILD ARCTIC CLIMATES. 



193 



that there has sometmies been a greater extension of the Antarctic 

 lands during Tertiary times ; and it is therefore not improbable 

 that a more or less glaciated condition may have been a long 

 persistent feature of the southern hemisphere, due to the 

 peculiar distribution of land and sea which favours the pro- 

 duction of ice-fields and glaciers. And as we have seen that 

 during the last three million years the excentricity has been 

 almost always much higher than it is now, we should expect 

 that the quantity of ice in the southern hemisphere will usually 

 have been greater, and will thus have tended to increase the force 

 of those oceanic currents which produce the mild climates of 

 the northern hemisphere. 



Evidences of Climate in the Secondary and Palceozoic epochs. — 

 We have already seen, that so far back as the Cretaceous period 

 there is the most conclusive evidence of the prevalence of a 

 very mild climate not only in temperate but also in Arctic lands, 

 while there is no proof whatever, or even any clear indication, 

 of early glacial epochs at all comparable in extent and severity 

 with that which has so recently occurred ; and we have seen 

 reason to connect this state of things wdth a distribution, of 

 land and sea highly favourable to the transference of warm water 

 from equatorial to polar latitudes. So far as we can judge by 

 the plant-remains of our own country, the climate appears to 

 have been almost tropical in the Lower Eocene period ; and as 

 we go further back we find no clear indications of a higher, but 

 often of a lower temperature, though always warmer or more 

 equable than our present climate. The abundant corals and 

 reptiles of the Oolite and Lias indicate equally tropical condi- 

 tions ; but further back, in the Trias, the flora and fauna become 

 poorer, and there is nothing incompatible with a climate no 

 warmer than that of the Upper Miocene. This poverty is still 

 more marked in the Permian formation, and it is here that 

 clear indications of ice-action are found in the Lower Permian 

 conglomerates of the west of England. These beds contain 

 abundant fragments of various rocks, often angular and some- 

 times weighing half a ton, while others are partially rounded, 

 and have polished and striated surfaces, just like the stones of 

 the " till." They lie confusedly bedded in a red unstratified marl, 



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