Nowhere else does the Balkan peninsula exhibit such varied features as on the shores of the Ægean Sea, and of the adjoining basin of the Sea of Marmara. Bluffs, hills, and mountain masses rise abruptly from the plain; arms of the sea extend far inland; and ramified peninsulas project into the deep waters of the ocean. It appears almost as if nature were making an effort to create an archipelago similar to that in the south. The tongue of land upon which Constantinople has been built offers a remarkable example of the features which characterize the coast lands of this portion of Europe. Geologically the whole of this peninsula belongs to Asia. Its hollow hills are separated from the granitic mountains of Europe by a wide plain covered with recent formations, and the wall of Athanasius, now in ruins, which was built as a defence to the city, approximately marks the true boundary between Europe and Asia. The rocks on both sides of the Bosphorus belong to the Devonian formation. They contain the same fossils, exhibit the same outward aspects, and date from the same epoch. A patch of volcanic rocks at the northern entrance to the Bosphorus likewise exhibits the same characteristics on both sides of the strait, and there cannot be the least doubt that this European peninsula at a former epoch constituted a portion of Asia Minor, but was severed from it by an irruption of the waters. [Illustration: THE CITY OF CONSTANTINOPLE, AND THE THRACIAN BOSPHORUS.] [Illustration: CONSTANTINOPLE AND THE GOLDEN HORN, FROM THE HEIGHTS OF EYUB.]