In the European ocean of the Azoic epoch we find five islands of considerable size.  The largest of these is at the North.  Scandinavia had even then almost her present outlines; for Norway, Sweden, Finland, and Lapland, all of which are chiefly granitic in character, were among the first lands to be raised.  Between Sweden and Norway, there is, however, still a large tract of land under water, forming an extensive lake or a large inland sea in the heart of the country.  If the reader will take the trouble to look on any geological map of Europe, he will see an extensive patch of Silurian rock in the centre of Sweden and Norway.  This represents that sheet of water gradually to be filled by the accumulation of Silurian deposits and afterwards raised by a later disturbance.  There is another mass of land far to the southeast of this Scandinavian island, which we may designate as the Bohemian island, for it lies in the region now called Bohemia, though it includes, also, a part of Saxony and Moravia.  The northwest corner of France, that promontory which we now call Bretagne, with a part of Normandy adjoining it, formed another island; while to the southeast of it lay the central plateau of France.  Great Britain was not forgotten in this early world; for a part of the Scotch hills, some of the Welsh mountains, and a small elevation here and there in Ireland, already formed a little archipelago in that region.  By a most careful analysis of the structure of the rocks in these ancient patches of land, tracing all the dislocations of strata, all the indications of any disturbance of the earth-crust whatsoever, Elie de Beaumont has detected and classified four systems of upheavals, previous to the Silurian epoch, to which he refers these islands in the Azoic sea.  He has named them the systems of La Vendee, of Finistere, of Longmynd, and of Morbihan.  These names have, for the present, only a local significance,—­being derived, like so many of the geological names, from the places where the investigations of the phenomena were first undertaken,—­but in course of time will, no doubt, apply to all the contemporaneous upheavals, wherever they may be traced, just as we now have Silurian, Devonian, Permian, and Jurassic deposits in America as well as in Europe.

The Silurian and Devonian epochs seem to have been instrumental rather in enlarging the tracts of land already raised than in adding new ones; yet to these two epochs is traced the upheaval of a large and important island to the northeast of France.  We may call it the Belgian island, since it covered the ground of modern Belgium; but it also extended considerably beyond these limits, and included much of the Northern Rhine region.  A portion only of this tract, to which belongs the central mass of the Vosges and the Black Forest, was lifted during the Silurian epoch,—­which also enlarged considerably Wales and Scotland, the Bohemian island, the island of Bretagne, and Scandinavia.  During this epoch the sheet of water between Norway