Identifier: islandlifeorphen001wall (find matches)
Title: Island life : or, the phenomena and causes of insular faunas and floras, including a revision and attempted solution of the problem of geological climates
Year: 1911 (1910s)
Authors: Wallace, Alfred Russel, 1823-1913
Subjects: Biogeography Islands Glacial epoch
Publisher: London : Macmillan
Contributing Library: California Academy of Sciences
Digitizing Sponsor: California Academy of Sciences Library

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theeffect if the Antarctic continent, instead of being confinedalmost wholly within the south polar circle, were to extendin one or two great mountainous promontories far into thetemperate zone ? The comparatively small Heard Islandin S. Lat. 53° is even now glaciated down to the sea. Whatwould be its condition were it a northerly extension of alofty Antarctic continent? We may be quite sure thatglaciation would then be far more severe, and that an ice-sheet corresponding to that of Greenland might extend tobeyond the parallel of 50° S. Lat. Even this is probablymuch too low an estimate, for on the west coast of NewZealand in S. Lat. 43° 35 a glacier even now descends towithin 705 feet of the sea-level; and if those islands werethe northern extension of an Antarctic continent, we maybe pretty sure that they would be nearly in the ice-covered condition of Greenland, although situated in thelatitude of Marseilles. ^ On the Glacial Epoch, by James Croll. Geol. Magi July, August,1874.
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CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 139 Conditions Determining the Presence or Absence of Perpet-ual Snow.—It is clear, then, that the vicinity of a sea or oceanto supply moisture, together with high land to serve as acondenser of that moisture into snow, are the prime essen-tials of a great accumulation of ice ; and it is fully inaccordance with this view that we find the most undoubtedsigns of extensive glaciation in the west of Europe and theeast of North America, both washed by the Atlantic andboth having abundance of high land to condense themoisture which it supplies. Without these conditionscold alone, however great, can produce no glacial epoch.This is strikingly shown by the fact, that in the verycoldest portions of the two northern continents—EasternSiberia and the north-western shores of Hudsons Bay—there is no perennial covering of snow or ice whatever.No less remarkable is the coincidence of the districts ofgreatest glaciation with those of greatest rainfall at

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