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Show 1G4 ISLAND LIFK (PAl{'!' I, and some of them can be traced to the Wel:lh 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 o~ly possible explanation, that, with our present knowledge, we can givo of them. Permian breccias are also found in Ireland, containing blocks of Silurian and Old Red sandstone rocks which Professor Hull believes could only have been carried by floating ice. Similar breccias occur in the south of Scotland, and these are stated to be "overlain by a deposit of glacial age, so similar to the breccia below as to be with difficulty distinguished from it." 1 _ These numerous physical indications of ice-action over a considerable area during the same geological period, coinciding ·with just such a poverty of organic remains as might be produced by a very cold climate, are very important, and seem clearly to indicate that at this remote period geographical conditions were such as to bring abont a glacial epoch in our part of the world. Boulder-beds also occur in the Carboniferous formation, both in Scotland, on the continent of Europe, and in North America ; and Professor Da.wson considers that he has detected true glacial deposits of the same age in Nova Scotia. Boulder-beds also occur in the Silurian rocks of Scotland and North Ameril:a, and according to Professor Dawson, even in the Huronian, older than our Cambrian. None of these indications are however so satisfactory as those of Permian age, where we have the very kind of evidence we looked for in vain throughout the whole of the Tertiary and Secondary periods. Its presence in several localities in such ancient rocks as the Permian is not only most important as indicating a glacial epoch of some kind in Palreozoic times, but confirms us in the validity of our conclusion, that the total absence of any such evidence throughout the Tertiary and Secondary epochs demonstrates the absence of recurring glacial epochs in the northern hemisphere, notwithstanding the frequent recurrence of periods of high excentricity. 1 Geological Magazine, 1873, r. 320. Cf!AP. lX.) GEOLOGICAL CLIMATES. 195 --------------------------------------- WaTm A1·ctic Climates in ea1·ly SecondaTy and Palceozoic times. -The evidence we have already adduced of the mild climates prevailing in the Arctic regions throughout the Mi~cene, Eocene, and Cretaceous periods is supplemented by a considerable body of facts relating to still earlier epochs. In the Jurassic period, for example, we ha;re proofs of a. mi~d Arctic climate, in the abundant plant-remams of East Sibena and Amurland, with less productive deposits in Spitzbergen, and at Ando in Norway just within the Arctic circle. But even more remarkable are the marine remains found in many places in high northern latitudes, among which we may especially mention the numerous ammonites and the vertebrre of huge reptiles of the genera Ichthyosaurus and .Tele~saurus found in the Jurassic deposits of the Parry Islands m 77 N. Lat. In the still earlier Triassic age, nautili and ammonites inhabited the seas of Spitzbergen, where their fossil remains are now found. In the Carboniferous formation we again meet with plant-remains and beds of true coal in the Arctic regions. Lepido.dendrons and Calamites, together with large spreading ferns, are found at Spitzbergen, and at Bear Island in the extreme ·north of Eastern Siberia; while marine deposits of the same aO'e contain abundance of large stony corals. 0 Lastly, the ancient Silurian limestones, which are widely spread in the high Arctic regions, contain abundance of corals and cephalopodous mo1lusca resembling those from the same deposits in more temperate lands. . Conclusions as to the Olirnates of Te1·tiary and Secondary perwds. -If now we look at the whole series of geological facts as to the animal and vegetable productions of the Arctic regions in past ages it is certainly difficult to avoid the conclusion that they indicate a climate of a uniformly temperate or warm charact~r. Whether in Miocene, Upper or Lower Cretaceous, Jurassic, Triassic, Carboniferous or Silurian times, and in a.ll the numerous localities extending over more than half the polar regions, we find one uniform climatic aspect in the fossils. This is quite inconsistent with the the?ry of alternate cold and mild epochs during phases of high excentricity, anci 0 2 |
