The Macaluba, in Sicily, which owes its name to the Arabs, is the mud volcano most anciently known. It is mentioned by Plato in his ‘Phædon,’ and has been described by Strabo. It is situated five miles to the north of Girgenti, on a hill of a conical shape, truncated at the top, and 150 feet high. The summit is a plain half a mile round, and the whole surface is covered with thick mud. The depth of the mud, which is supposed to be immense, is unknown. There is not the slightest appearance of vegetation upon it. In the rainy season the mud is much softened; the surface is even, and there is a general ebullition over it, which is accompanied with a very sensible rumbling noise. In the dry season the mud acquires greater consistency, but its motion still goes on. The plain assumes a form somewhat convex; a number of little cones are thrown up, which rarely rise to the height of two feet. Each of them has a crater, where black mud is seen in constant agitation, and incessantly emitting bubbles of air. With these the mud insensibly rises, and as soon as the crater is full of it, it disgorges. The residue sinks, and the cone has a free crater, until a new emission takes place. Such is the ordinary state of the Macaluba; but from time to time the hill becomes subject to alarming convulsions. Slight earthquake shocks are felt at the distance of two or three miles, accompanied with internal noises resembling thunder. These increase for several days, and are followed at last by a prodigious spout of mud, earth, and stones, which rises two or three hundred feet in the air. Similar paroxysmal explosions have been observed in the Caucasian mud volcanoes. In February 1794, the Obu, in the peninsula of Taman, had an eruption accompanied with a dreadful noise, and an earthquake which radiated from the cone, and was felt as far as Ekaterinodor, at a distance of fifty-five leagues. At the beginning of the eruption flames were seen, which rose to a prodigious height, and lasted about half an hour. At the same time dense clouds of smoke escaped from the crater, and mud and stones were cast up to the height of 3,000 feet. Six streams of mud, the largest of which was half a mile long, flowed from the volcano, and their volume is said to have been equal to twenty-two millions of cubic feet. Violent eruptive symptoms accompanied the formation of a new mud volcano in the vicinity of Baku on the Caspian. On November 27, 1827, flames blazed up to an extraordinary height for three hours, and continued for twenty hours more to rise about three feet above a crater from which mud was ejected. At another point in the same district, where flames issued, fragments of rock, of large size, were hurled up into the air and scattered around.