Page:The Zoologist, 3rd series, vol 1 (1877).djvu/175

Rh retired to the south as the glacial period set in, again returned to their former haunts, whilst not a few became extinct.

Finally, Period IV.—After an interval, more or less lengthened, the ultimate separation of the British Islands from the European Continent, and of Ireland from England took place, resulting in the geographical outline now delineated in a map of Europe.

Unreckoned ages are included in these changes, and no one can form even an approximate idea, according to modern computation, of their extent or duration.

 

at a map of Donegal will show that it is a county of considerable extent, generally very hilly, and with a coast line of most irregular character. Lough Swilly, Mulroy Bay, and Sheephaven are arms of the sea penetrating southward from the Atlantic from twelve to sixteen miles, and modifying the climate so much that when snow falls, as it does very rarely, it never lies, but disappears in a very short time. These deep-sea fiords, with their rich marine fauna and flora, the coast outside beaten by the Atlantic surge, the numerous fresh-water loughs—many of them of considerable size—the bogs, mountains, marshes, sands, and cultivated grounds, present such a variety of conditions as is most favourable to the student of Natural History. I propose briefly giving some account of the Geology, Botany, Zoology, and Archæology of the district.

The primary and melamorphic rocks form the backbone of the County Donegal. In very local patches, and in small quantities, the more valuable minerals and metals occur. Lead, copper, silver and gold have been found, but so sparingly as would not repay the expense of working. The post-tertiary deposits are everywhere met with, and are often full of interest. The boulder clay is very 