We have already spoken of the two principal groups of extinct craters which exist in the central portion of Madagascar. In the more southerly of these groups, Dr Mullens speaks of an ascent of Ivòko, one of the finest old volcanoes, which is eleven hundred and thirty feet high. This, he says, “was a vast crater, a quarter of a mile across; the encircling wall was complete except at the south, where the opening was fifty feet wide. Beneath us, half-a-mile to the east, was another crater, Iatsìfitra, second only to Ivòko, with its opening to the north. On the north-west shoulder of Ivòko were two other large craters, overhanging the village of Bétàfo, two more were close by to the north-east, and others were conspicuous ten miles to the north. On the south again were several others, the horseshoe shape being very marked in them all. Descending to the crater of Iatsìfitra, we observed that the lava rocks which had issued from it were black, sharp and fresh, as if they had been broken yesterday. On the plain I counted thirty greater piles of lava, like ruined fortresses, and numberless smaller ones. It was clear that like the Phlegræan fields in Italy, the entire plain had at some time been on fire; and that a hundred jets of flame and molten lava had spurted from its surface, hurling their blazing rockets into the sky. Altogether, in our journey to the west and south-west of the capital, we counted a hundred extinct craters, extending over an arc of ninety miles.” [Sidenote: A VOLCANIC BELT] Madagascar appears, therefore, to be the extinct central portion of a volcanic belt which extends from Great Comoro to the north-west, through the other islands of the group, Nòsibé and northern and central Madagascar, to Réunion to the east, a distance of thirteen hundred and sixty miles. And it is noteworthy that at each extremity of this belt there is a still active volcano—viz. Piton de Fournaise, in Réunion, and one eighty-five hundred feet high in Great Comoro. [Sidenote: EARTHQUAKES]