373 



NATURE 



\A7igust 14, 1875 



is the great mass of elevated peaks called Ankh.ratra, in 

 the central province. This has hardly the grand appear- 

 ance of Mount Amber (although it considerably exceeds 

 the latter in absolute height), since it rises from the 

 elevated region of Imdrina, which is at the capital 

 about 4,000 feet above the sea-level. Ankkratra is never- 

 theless a noble group of hills, and is the most conspicuous 

 feature of the landscape over a considerable portion of 

 the central regions of the island. There are five or six 

 principal summits, which vary from 8,000 to 9,000 feet in 

 height, the most lofty one, a peak called TsikfajJivona 

 (" that which the mists cannot climb"), being 8,950 feet 

 above the sea-level, and is the highest point in the island. 



Another interesting physical feature of Madagascar, 

 ■which has only been made clear very recently, is the 

 existence of an almost continuous belt of virgin forest all 

 ground the island, and generally following the coast-line. 

 This forest-belt divides into two on the eastern side of 

 the country, leaving a long narrow valley about 250 miles 

 long between the two lines. The uppermost of these 

 •clothes the slopes which form the edge of the upper 

 plateau of the island. North of this valley the two lines 

 ■unite, and here is the widest portion of the forest, it being 

 about forty miles across. The average breadth is from 

 fifteen to twenty miles. On the north-west side the forest 

 is not continuous, but the extremities overlap about 100 

 miles, leaving an opening seventy miles wide. The total 

 length of this forest must be about 2,300 miles, and much 

 of this is yet unexplored, so that there is doubtless still 

 much of interest in botanical science awaiting research. 

 Besides the forest-belt a good deal of the plain country to 

 the west is well wooded. 



A third fact of interest in the physical geography of 

 Madagascar is the evidence of recent volcanic action 

 Shroughout a great part of the country. It has been 

 known for several years that there were signs of this on 

 the north-west coast, and that in the island of Nosib(f 

 <ind the adjacent mainland there are numerous extinct 

 craters and much igneous rock. A few years ago the 

 Rev. T. Campbell pointed out evident traces of volcanic 

 agency in the district near the Ank^ratra hills. He says : 

 ■" It seemed as if the whole place were once a great 

 smeltery, from the enormous number of clinkers lying 

 about. There are altogether five mountains all near to 

 each other, which have been active volcanoes at some 

 remote period ; each has one of its sides melted down 

 and the inside hollowed out. The flow of lava looks as 

 if it had been some immense reservoir bursting its banks, 

 and the water dashing and foaming through, bearing 

 everything away with it, or covering the plain beneath." 



In a journey I took to the Lake Itilsy in 1866, I was 

 struck with the number of truncated cones in the hills 

 surrounding the lake. But extensive journeys made more 

 recently in various directions have revealed the existence 

 of a very widespread and powerful subterraneous action, 

 probably extending almost unbroken from the south-east 

 to the north-west and extreme north of Madagascar. There 

 seems reason to suspect that this volcanic belt is part of 

 a line which has its eastern extremity in the island of 

 Reunion, where there is a volcano still showing occasional 

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

 tremity passes through the Comoro Group (the islands of 

 which consist of grand masses of lofty volcanic moun- 

 tains), and terminates in the island of Great Comoro, 

 where also, as in Rdunion, 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 Mada- 

 gascar 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 It^sy. These are thus described by Dr. Mullens :— | 

 " When we ascended the lofty hill overhanging the west- 

 ern end of the lake, crater after crater met our astonished | 

 gaze. There were forty in all, of which we were sure ; 

 we think there were others beyond to the north." " Fifty 

 miles further south we came on the volcanoes again. We 

 climbed a lofty rounded hill called Ivoko, 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 being 1,100 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, latslfitra, 

 had its opening towards 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, and ruined palaces. I counted 

 thirty greater piles, and noted numberless smaller ones ; 

 it was clear that at one time the entire plain had been on 

 fire, that a hundred jets of fire and flame and molten lava 

 had spurted from its surface. The heaps were now old 

 and moss-grown, but we were informed of a vague tradi- 

 tion among the people that their ancestors had seen these 

 flames bursting forth. Altogether, in that important 

 journey, we saw and counted a hundred extinct craters, 

 extending over an arc of ninety miles, not reckoning the 

 central mass of AnkJiratra, round one side of which that 

 arc bends." ' 



In a journey to the south-east of Madagascar I dis- 

 covered traces of volcanic action in many places ; in 

 some parts shown by the deposits of rolled pebbles of 

 lava, and in others by the streams of lava rock running 

 into the sea and forming reefs which were gradually being 

 broken up by the surf. And in the very opposite part of 

 the island, on the extreme north-west coast opposite the 

 Minnow group of islets. Bishop Kestell-Cornish ob- 

 serves : — " This coast is the most distinctly volcanic that 

 I have seen in Madagascar ; at one point the lava must 

 have run down to be quenched in the sea, and it looked 

 as if this had taken place only last year." 



In the Antsihknaka province also the same plutonic 

 agency is distinctly visible. A great part of this region 

 consists of an immense marshy plain, about forty miles 

 long by twenty wide, with the lake Alaotra at its north- 

 east corner, and surrounded by hills ; and it has evidently 

 been the seat of some powerful subterranean force by 

 which this depression was caused. This is clear from the 

 fact that the lines of hills which are seen on both sides 

 the AntsihJmaka plain do not run in the same direction as 

 the main valley or depression of the country, but cut it at 

 an angle of about 45°. Many of the ridges seem to be 

 broken off more or less abruptly by the level ground for 

 several miles, and then are continued on the other side of 

 the plain. It seemed impossible to avoid the conclusion 

 that by some great convulsion a vast rent and depression 

 had been made across the lines of hills in a diagonal 

 direction ; while the water-worn remains of some of these 

 toward the south, forming a line of low detached hills, 

 suggested that the action of water, either as an arm of the 

 sea or a great river, had completed what was commenced 

 by more violent agencies. The evidence of former vol- 

 canic action in the presence of extinct craters and lava 

 streams to the west, north, and north-east of the plain, 

 gives considerable support to this supposition. 



About a hundred miles north of the Antsih^naka pro- 

 vince there seem to be further traces of the same agency. 

 The Rev. J. A. Houlder thus describes a remarkable 

 valley called Mkndritsira, which, until he saw it in 1876, 

 was unknown to Europeans even by name, and not 

 marked upon any map :— "It is a great basin, or rather a 

 mighty elongated pit, sunk deep down among the sur- 

 rounding heights. It is about thirty miles long and 



' Proc. Roy. Gcogr. Soc, January 23, 1875, 'pp. 187, j88. 



