200 



ISLAND LIFE 



PART I 



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 com- 

 parable in extent and severity with that which has so 

 recently occurred ; and we have seen reason to connect this 

 state of things with 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 coimtry, 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 conditions ; but further back, in the Trias, the 

 flora and fauna, in the Brittish area, 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 some 

 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 

 sometimes 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, and some of them can be traced to 

 the Welsh hills from twenty to fifty miles distant. This 

 remarkable formation was first pointed out as proving a 

 remote glacial period, by Professor Ramsay ; and Sir Charles 

 Lyell agreed that this is the only possible explanation 

 that, with our present knowledge, we can give of them. 



Permian breccias are also found in Ireland, containing 



