MAUNA LOA. 135 



thirty or forty feet high, which are apparently bound down by huge 

 tortuous masses, which surround them like cables. In other places 

 these are stretched lengthwise on the level ledge, and look like hideous 

 fiery serpents with black A'itreous scales, that occasionally give out 

 smoke, and in some cases fire. 



The immense space which I have described the crater as covering, 

 is gradually filled with the fluid mass of lava to a certain point, above 

 which the walls, or the surrounding soil, are no longer able to 

 bear the pressure. It then finds vent by an eruption, previous to 

 which, however, a large part that is next to the walls of the crater 

 has in a measure become cooled, and remains fixed at the level it had 

 attained. After the eruption, the central mass therefore alone sub- 

 sides three or four hundred feet, and leaves the portion that has 

 become solid, forming a kind of terrace or shelf: this is what consti- 

 tutes the "black ledge," and is one of the most striking features of 

 the crater. Its surface is comparatively level, though somewhat 

 uneven, and is generally coated with a vitreous and in some places a 

 scoriaceous lava, from half an inch to an inch thick, very iridescent 

 and brittle. In walking over this crust, it crumbles and cracks under 

 the feet ; it seems to be easily decomposed, and in some places had 

 lost its lustre, having acquired a grayish colour and become friable. 

 There was another variety of the vitreous lava, which was smooth 

 and brittle : this occurred in the large hollow tunnels or trenches, the 

 insides of which were rough, and full of sharp and vitreous points. 

 On the turnings and windings small swellings were met, which on 

 being broken off, had a strong resemblance to the bottom of a junk- 

 bottle ; at another place, fragments appeared to have been scattered 

 around in a semi-fluid state, in an endless variety of shapes, and so 

 brittle as to be preserved with difiiculty. Underneath these was to be 

 seen the real lava or basalt, as firm and solid as granite, with no ap- 

 pearance of cells, and extremely compact ; it is seen separated into 

 large blocks, but none that I saw were of a regular figure, though 

 in some places it was thought by others to approach the hexagonal 

 form. 



There is a third kind of lava, fibrous in its texture, of quite recent 

 ejection, and procured from the bottom of the crater : this had some- 

 what the appearance of a dark pumice, but was dense in comparison. 

 On the black ledge the absence of all debris from those high perpen- 

 dicular walls, cannot fail to be remarked ; we endeavoured to find an 

 explanation of this, but I was not satisfied with the only one which 

 presented itself This was to suppose that the fluid mass had recently 



