28 EXTINCT VOLCANOES. 



a very widespread and powerful subterranean action through- 

 out a great part of the island, probably extending almost 

 unbroken from the south-east to the north-west and extreme 

 north. There seems reason to believe that this volcanic belt 

 is part of a line which has its eastern extremity in the island 

 of Eeunion, where there is a volcano still showing occasional 

 signs of activity ; while the other (north-western) extremity 

 passes through the Comoro group (the islands of which consist 

 of grand masses of lofty volcanic mountains), and terminates 

 in the island of Great Comoro, where also, as in Eeunion, is 

 a still active volcano. It would seem as if the subterranean 

 forces had expended their energy in the intermediate space, 

 for there is no active volcano in Madagascar, while at each 

 end of the line their presence is still occasionally felt. There 

 are, however, signs of not altogether extinct forces in the 

 slight earthquake-shocks which are felt almost every year, 

 and in the hot springs of various kinds which occur in many 

 parts of the country. 



A large number of extinct volcanoes are found west of 

 Lake Itasy. These are thus described by Dr. Mullens : 

 " When we ascended the lofty hill overhanging the western 

 end of the lake, crater after crater met cur astonished gaze. 

 Some were of enormous size, some were small ; some were 

 cones, others were hollow, or were horseshoe in shape, and 

 had long ridges of lava running out from the open side. 

 There were forty craters in all, of which we were sure ; we think 

 there were others beyond to the north." " Fifty miles farther 

 south we came on the volcanoes again. We climbed a lofty 

 rounded hill called Ivdko, and then found that we were on 

 the crater wall. The inner hollow was a quarter of a mile 

 wide, the height of the wall above the level country outside 

 was iooo feet. Two lava streams went out towards the 

 south and west; three small craters were at the foot, and 

 others, large and conspicuous, were around us on every side. 

 Close by, another huge crater, Iatsifitra, had its opening to- 

 wards the north, and the lava that had issued from it was 

 fresh, black, and sharp, as if broken yesterday. But stranger 

 still, at its eastern side was a plain a mile square, covered 

 with heaps of lava like stone cottages, fortresses, ruined 



