466 MAJOR H. DE HAGA HAIG ON THE [Aug. 1895,. 



caves, and here and there one meets with strange phenomena. At 

 Vacoas there are a number of caves of no great extent, but many of 

 them contain water, often affording the only supply of that necessary of 

 life to the inhabitants of the surrounding district. Not far away is 

 one of the most striking examples of a river flowing some distance 

 underground, at a spot called l'Eau Coulee. It is about 2 miles 

 from Curepipe, on the Port Louis road. Within a stone's-throw of 

 the highway on the right, runs a main tributary of the Grand river 

 N.W., at this point the size of a fair trout-stream, in a shallow 

 wooded gully. It enters a cavern through the centre of a lava- 

 flow, high enough to walk into. The roof is broken through in 

 four more places lower down, at one of which another stream comes 

 in from another cave ; and, finally, a hundred yards or so away 

 there is a deep pool in which the water can be seen welling up,, 

 carrying sticks and leaves with it, and thence it flows off over 

 a rocky course into a ravine. It appears strange that another 

 stream should rise close to the mouth of the cavern, run within 

 10 feet of the river in the cavern, and then diverge and disappear 

 amongst the rocks, probably feeding the tributary stream in the 

 cavern. It is a fact worth noting that one of the openings in 

 the roof of the cavern was ' burst up ' by the water, during the 

 hurricane in February 1876, and this probably furnishes a clue for 

 the explanation of the fact that so many of the caves amongst the 

 lava-flows are broken through. 



Between the Corps de Garde mountain and Montagne Ory s . 

 at a place called Petite Riviere, there is a beautifulty perfect cave, 

 like a railway-tunnel, in solid lava, with ledges of the same a few 

 feet above the ground, running along the sides. The cave is about 

 30 feet high and the same wide, with an arched roof. The writer 

 followed this cavern for 1 g mile, until he found it nearly filled up by 

 detritus brought in by a stream, whose bed was well-marked. A 

 current of air passed through downwards, and, as on the coast 3 miles 

 away there are lava-cliffs full of caves, it seems probable that this 

 cavern communicates with some of them. 



It is difficult to account for the origin of caves of this description ; 

 probably they are formed somewhat in this manner : — A slowly 

 flowing lava-stream descends a gentle slope ; it reaches a steeper 

 descent and its flow is accelerated ; the centre, the most liquid part, 

 is drawn out, leaving the cooled and hardened roof and sides, its 

 place being taken by steam and other gases given off by molten 

 lava. The bubbly lava-drops from the roof and on the walls 

 would thus be explained, and the ledges would represent levels at 

 which the lava stood longer than usual. Or these caves might be 

 caused by the molten centres of lava-streams flowing on after the 

 supply from the craters had ceased, and thus leaving hollows behind 

 them. In the Petite Riviere cavern there are seven ledges dis- 

 tinguishable, all very scoriaceous. The upper one is covered with 

 layers of lava which appear to have trickled down the walls. This 

 theory explains why the roof, sides, and floor are all in one mass 

 of solid rock, which it would be difficult otherwise to account for. 



