500 Mr. Burr on the Geology of Aden, 



vated above the general level of the ocean. The most interesting portion of the 

 promontory is however an immense volcanic crater, which is situated at the ex- 

 tremity next the main land, and in the very centre of which the town of Aden 

 with the British cantonment stands. This magnificent crater is nearly circular in 

 form ; its diameter is probably about a mile and a half, and it is surrounded on 

 the northern, western, and southern sides with precipices chiefly composed of 

 lava, and rising from 1000 to 1776 feet in height, the latter elevation being that of 

 the " Gebel Shunsam," a lofty range of volcanic peaks, which form the crater's 

 western side. On the eastern side the wall of the crater has subsided or been 

 broken down for about half a mile, thus allowing the sea to come almost close 

 to the town, and forming a small bay, generally occupied by native Arab vessels. 

 Still however the lofty and abrupt island of " Seerah," about the middle of the gap, 

 serves as it were to connect the broken portions, and almost to complete the ori- 

 ginal circle of the crater. Northward of this great focus of eruption, and ranging 

 to the extremity of the promontory, is an immense mass of lofty and jagged rocks, 

 all composed of lava. They have indeed much the appearance of a cluster of 

 smaller volcanic craters, the sides of which have been washed away to the eastward 

 by the action of the sea ; but on this portion of the promontory, I was able to 

 bestow but a slight and hurried examination. 



The interior of the great crater in which the town of Aden stands, presents 

 almost a flat surface, and is not elevated very much above the sea-level, the vol- 

 canic orifice appearing to have been filled up so far, partly by the crumbling in of 

 the sides, and partly by the matter which may have washed in from the sea. The 

 crater itself, though at first sight almost perfect, has manifestly undergone some 

 rude shocks, the effects of which are very apparent on examination. It has in fact 

 been cleft entirely through in one direction and partially so in another ; a great 

 fissure ranges across it from north to south, and the two rents formed by it in 

 the walls are called the " northern " and " southern passes," the former of which 

 being very important in a mihtary point of view, as it affords the principal in- 

 gress, is strongly fortified. The western half of the crater stands entire, forming 

 the " Gebel Shunsam," which, as already noticed, is 1780 feet in height, and has 

 within it a curious ledge of rocks about half its own elevation, which I had not 

 time to examine. The eastern half of the crater has evidently undergone a partial 

 subsidence ; as it does not rise to more than half the height of the western side, and 

 it appears to have separated in two parallel lines at right angles to the great north 

 and south fissure. It is on the line of these subordinate fissures, that the sea, as 

 before noticed, has broken in, and between them stands the island of " Seerah," 

 which, although left as it were without support on both sides, has itself very slightly 

 subsided. 



While viewing the grand disruptions of this great volcanic mass, which although 



