island and Norway; the soundings being respectively 2650 and 1760 fathoms.[1] The elevation of this tract of land would afford a means of free migration of animals, and plants from Europe to America, or from America to Europe. I have therefore taken the 500-fathom line to mark the probable boundary of the Eocene Atlantic, as well as the southern extension of the Eocene North Sea in the direction of the Shetlands. The enormous depth of the Atlantic between Ireland and the United States forbids the hypothesis that the line of communication was in that direction.
From these considerations Eocene Britain may be taken to have formed part of a great continent, extending northwards and westwards to America by way of Iceland and Greenland, while to the north-east it was continuous with Norway and Spitzbergen. It extended also to the south-west, across what is now the Channel, to join the western parts of France. This great north-western continent, or northern Atlantis as it may be termed, existed through the Eocene and Meiocene ages, offering a means of free migration for plants and animals, and it was not finally broken up by submergence, as we shall see in the course of this work, until the beginning of the Pleiocene age.
The Mountains.
The highlands of Britain in the Eocene age were in their present positions. The older Palæozoic strata of Cornwall, Wales, Cumberland, and Scotland had already been cut up into hill and valley before the deposit of the Triassic rocks, and constituted a broken chain of
