244 
DR. DAVY’S ACCOUNT OF A NEW VOLCANO 
by the magnet. None effervesced with acids ; all were readily fusible be- 
fore the blowpipe, and ran into a black or dark green glass. I could not detect 
in any of them the smallest trace of carbonaceous matter, or any free acid, 
or alkali, or uncombined alkaline earth. From experiments which I made on 
small portions of each kind, they all appeared to consist of alumine, lime, mag- 
nesia and silex coloured by protoxide of iron, and without any potash. The 
absence of crystalline structure was very remarkable in all of them, with the 
exception of the small masses, already alluded to, of vesicular lava *. 
I have already mentioned that I was indebted to Captain Wodehouse for 
a specimen of the water of the crater, taken up soon after it had become 
tranquil, and when its temperature was 200°. He furnished me with three 
wine-bottles full, — one of them from that part of the crater which was almost 
separated from the main crater by a bar of cinders, and was called the “ small 
crater,” and two from the main crater. They were well secured with corks. 
The specific gravity of the water from the “ small crater” was 1*057 ; that 
of one from the main crater was T069, and that of the other T0/0. In pro- 
perties and composition they appeared to be very similar. They were free from 
any odour, of a dirty fawn colour, from a fine dust which was suspended in 
them, and which on rest subsided ; after which they became perfectly clear 
and colourless. 
The sediment obtained by filtering the water from the main crater (about 
three pints) weighed thirty grains. It consisted of a light brown ochrey pow- 
* Since writing the above, I have been favoured by Captain Senhouse with four specimens of rock 
ejected by the volcano, which from their nature it may be inferred were thrown up from the bed of 
the sea. Three of these are water-worn pebbles, different varieties of limestone ; one of them is 
higldy crystalline dolomite, containing a considerable quantity of magnesia ; another is finely crystal- 
line, and contains a smaller proportion of magnesia ; and the third is of very fine grain, not crystalline, 
with only a trace of magnesia. The fourth specimen, wliich is a fragment of a mass said to have been 
of several pounds weight, has a good deal of the character of graywacke. It contains, disseminated 
through it, in a solid state, saline matter, chiefly common salt. It effervesces with acids, and gelati- 
nizes. From the few experiments I have made on it, it appears to be composed of a large proportion 
of silica, and of lime, magnesia, and alumine in about equal proportions, and to he coloured by prot- 
oxide of iron. Whether it contains any lime or magnesia not combined with carbonic acid, I have not 
ascertained. It is of considerable hardness and toughness, and is infusible before the blowpipe. Por- 
tions of its surface are covered with a vitreous fusible scoria, similar to that of the volcano, as if it had 
passed through, or come in contact with the fused matter of the volcano. 
