206 Transactions. — Geology. 



loose slags or hardened streams of lava, and whose summit 

 would have presented a rugged wall of scoria, forming the 

 rim of a mighty cauldron ; but instead of this we found our- 

 selves on the edge of a steep precipice, with a vast plain 

 before us, fifteen or sixteen miles in circumference, and sunk 

 from 200 ft. to dOOft. below its original level. The surface of 

 this plain was uneven, and strewed over with large stones and 

 volcanic rocks, and in the centre of it was the great crater, at 

 a distance of about a mile and a half from the walls of the 

 precipice on which we were standing. Our guides led us round 

 towards the north end of the ridge, in order to find a place by 

 which we might descend to the plain below. The steep down 

 which we scrambled was formed of volcanic matter, apparently 

 a light-red and grey kind of lava, vesicular, and lying in 

 horizontal strata, varying from 1 ft. to 40 ft. in thickness. In 

 a small number of places the different strata of lava were also 

 rent in perpendicular or oblique directions from the top to the 

 bottom, either by earthquakes or other violent convulsions of 

 the ground connected with the action of the adjacent volcano. 

 After walking some distance over the sunken plain, which in 

 several places sounded hollow under our feet, we at length 

 came to the edge of the great crater itself, where a spectacle 

 sublime and even appalling presented itself before us. Im- 

 mediately before us yawned an immense gulf, in the form of a 

 crescent, about two miles in length, from north-east to south- 

 west, nearly a mile in width, and apparently 800 ft. deep. 

 The bottom was covered with lava, and the south-western and 

 northern parts of it were one vast flood of burning matter, in 

 a state of terrific ebullition, rolling to and fro its fiery surge and 

 flaming billows. Fifty-one conical islands, so to speak, of 

 varied form and size, containing so many craters, rose either 

 round the edge or the surface of the burning lake. Twenty- 

 two of them constantly emitted columns of grey smoke or 

 pyramids of brilliant flame ; and several of these at the same 

 time vomited from their ignited mouths streams of lava, which 

 rolled in blazing torrents down their black indented sides 

 into the boiling mass below. The grey and calcined sides of 

 the huge crater before us ; the fissures which intersected the 

 surface of the plain on which we were standing ; the long 

 banks of yellow sulphur on the opposite side of the abyss ; the 

 vigorous action of the numerous small craters on its borders ; 

 the dense columns of vapour and smoke that rose at the north 

 and south ends of the plain ; together with the ridge of steep 

 rocks by which it was surrounded, rising probably, in some 

 places, 300 ft. or 400 ft. in perpendicular height, pre- 

 sented an immense volcanic panorama, the effect of 

 which was greatly augmented by the constant roaring of 

 the vast furnaces below." At night the grandeur of the scene 



