Excerpt from The Fauna of Scotland: With Special Reference to Clydesdale and the Western District, MammaliaThe facts indicated by the above Table are, at first sight, some what contradictory. As Ireland possesses the greatest number Of species in common with the mainland of Scotland, it might well be supposed to have been in connection with it up to a later date than even the Inner Islands. On the other hand we have the presence of other forms, as of the Field Vole in the Hebrides, and of the same species with the Water Shrew and Water Vole in Orkney, which are conspicuous by their absence from the Irish fauna. It appears to me, however, that this apparent contradic tion may be explained, if we remember the more northern position of the Scottish Islands and the nature of the country lying between them and the south-western source from which our Mammalian fauna was undoubtedly derived.A consideration of the relative depths of the channels which respectively divide Ireland and the Islands from the mainland of Scotland would lead us to the conclusion that the severance of the former took place first, and that the Orkneys remained longest uninsulated. An upheaval of about 240-2 70 feet would bring the latter again into communication with Caithness, while it would require a rise of about 300-320 feet to reunite the Hebrides with Skye, and of from 700 to 900 feet to restore land communication between the various parts of south-western Scotland and north eastern Ireland. Nor does the distribution of Mammal life seem to me to contradict such a hypothesis. The absence from the known fossil fauna of Scotland and Ireland of most of the characteristic postpliocene English animals shows that the north ward migration Of these forms was slow, gradually advancing as the glacial conditions of the northern parts of our islands decreased in intensity. Thus it is not difficult to suppose that the Hedge hog, Ermine, Badger, Squirrel, and Mountain Hare, may have found their way through southern Scotland into Ireland long before they were able to penetrate into the still sub-arctic regions of the Highlands. Subsequently, when the continued depression of the land had isolated Ireland, and the improvement of the climate had continued, the Shrews and Voles may well have found their way northwards along the comparatively genial coasts, before the larger beasts of prey could find a sufficient stock of game. When they reached Orkney, however, they appear to have found it a veritable Ultima Thule, for the absence from Shetland of any land animal (except the half-aquatic Otter) seems to indicate thatthose islands were already separated before the arrival Of any form of Mammalian life.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.