Europe, as a continent, is distinguished by its adjacent islands. Following the irregular coast-line of its many extremities, they lie along, in greater or less number, the satellites, so to speak, of the main land. They are scattered almost everywhere, yet not distant from the coast, like Iceland, but within sight of the shore. In character they resemble the adjacent coast, and form a true part of the main land, except in the one fact of separation. Strabo even called Sicily an insular continuation of Italy, and discriminated between islands found in mid-ocean and those found near the coast, calling the former pelagic and the latter littoral islands. These he regarded as having been at some previous period rent from the main land. The coast islands are by no means, like many of the pelagic islands, mere rocky groups, thrown up by volcanic convulsions, or small, desolate, barren ledges. They are very diverse in character: some are fertile single islands, like Sicily, Candia, Bornholm, Rugen, Negropont; some are double islands, like Britain and Ireland, Zealand and Funen, Corsica and Sardinia; some are island groups, like the 3 Balearic islands, the 3 Maltese islands, the 20 Ionian islands, the 67 Orkneys, the 90 Shetlands, the still more numerous Hebrides, the Aland group, and that of the Grecian archipelago. They are generally of very large size, in comparison with the continent to which they are adjacent; a characteristic not only very rare in islands, but which must exert great influence. They are to be viewed, therefore, as continuations of Europe, not as lands sundered from the main land; they are to be considered as its sea-ports, and the mediators between Europe and the other continents. In round numbers, the islands of Europe embrace about 175,000 square miles—a twentieth of the continent.