A F R - 1 N D I A N R E G I N S. 44] 



central pit having " four hundred feet" of additional depth, being 

 nearly at its lowest level on account of a recent emptying. 



On the 16th, I descended with others into the Great Crater, by the 

 usual path. On reaching the "black ledge," the lava-surface although 

 level was found to be by no means even ; the inequalities, a yard or 

 more high, instead of resembling waves, being more like overlapping 

 furrows, from the lifted edges of half congealed floes, and the piling 

 of superficial currents ; for in cooling, the lava passes slowly through 

 the semifluid state, continuing for a space to flow onwards; and end- 

 ing in a configuration of surface very unlike that of congealed water. 



Most of the lava of the " black ledge" was coated with a vitreous, 

 brittle, and scoriaceous crust, half an inch or so deep and easily de- 

 tached; which gives way and is crushed under the weight of the tra- 

 veller. While recent, this crust is black and shining, often of a pseudo- 

 fibrous texture that might be mistaken for crystalUne : but after years 

 of exposure on lava-streams, the crust loses its lustre, turns gray, and 

 at length decomposes and disappears. In accumulations of layers, 

 whether on the " black ledge" or elsewhere, I have found the crust 

 only on the surface of the uppermost layer. Cabinet specimens of 

 this crust sometimes pass for lava; whereas, the rock underneath is 

 the real lava, and is as heavy, solid, and enduring as granite or any 

 other kind of rock. I was almost startled by its resemblance to much 

 of the rock of ocean islands, both in the Atlantic and Pacific : the 

 contained cells being often irregular in shape, very thinly scattered, 

 or for considerable spaces wanting; leaving hardly any marked dis- 

 tinction from basalt. 



All over the surface of the island, the lava proved very uniformly 

 of the crusted kind : but on the " black ledge," currents were met with 

 of another kind of lava, smoothish externally and hard and solid 

 throughout ; yet withal somewhat vitreous, fragments having scaled off 

 from rapid cooling, as in the instance of imperfectly-annealed glass. 

 This variety of lava contained large ampulliie, or swellings that proved 

 to be hollow, with the lower surface somewhat re-entering, like the 

 bottom of a bottle; formed apparently by gaseous matter, and in larger 

 quantities than I was ever able to detect in watching volcanic action. 



Proceeding Westward over the "black ledge;" after making one- 

 fourth of its circuit, we arrived at a place where, during the recent 

 emptying, a lump of several acres had fallen into the central pit; the 

 original surface remaining intact, and inclining dowuAvards in a gradual 



111 



