Basaltic and trachytic hills, either isolated or in chains, rise at a distance of about half a mile from the sea-shore, which is winding and shelving. The hills are in general rounded, and marked by broad veins of similar composition, but containing more perfectly crystallised felspar, quartz, and zeolith. They have not the sharp peak, but are broken and cliffy, and have apparently been upheaved at different periods. On leaving the shore, a most striking specimen of columnar basalt presented itself in the ravine of Galeylafeo, which, for nearly half a mile, runs through the heart of a huge mountain. In width it is about 200 yards, and the perpendicular pillars are 200 feet in height. It is evident that water could not have been the sole agent in producing such a huge cleft, although at present the ravine presents the appearance of a regular water-course. The surrounding hills consist of the same rock, but covered with loose boulders, which are much stained with oxide of iron. Amongst the confusion of volcanic masses on the plain of Warelissan, excepting in some rare cases, when the true lava stream could be traced to its source, it was difficult to determine the exact site of the craters from whence they had been ejected. The hill which separates Bahr Assai from the sea, with its singular tops of limestone, slate, and creta, deserves a more minute examination than could be given at this season of withering heat. The western side is the most interesting, as being more open and disclosed; there is, however, as in all formations in the vicinity of volcanic countries, no uniform inclination of the layers. The range bordering the eastern shore of the lake is basalt and basaltic wacke; on the western, it is partly gypsum and limestone, but resting on basalt.