Page:Proceedings of the Royal Society of London Vol 1.djvu/443

Rh On the succeeding day, however, the eruptions were repeated with still greater violence than before; and the quantity of matter thrown up subsequent to this period was so great, that upon Capt. Tillard's return to St. Michael's on the 4th of July, one side of the cratu' was elevated nearly eighty yards above the level of the sea, and the circuit of it so nearly complete, that the channel .of communication between the inside and outside was not more than six yards over, and the water within was boiling hot. The beach was also proportionally heated; so that although by rowing round to the leeward side Capt. Tillard was able to land on the outer margin, the heat prevented his ascending at that part more than a few yards. The inclination also was so steep on all sides, as to occasion considerable difﬁculty in the attempt to reach the summit. The declivity below the surface of the sea was such, that at the distance of twenty or thirty yards the depth was found to be twenty—ﬁve fathoms.

A portion, about sixty feet in length, on one side of the opening being separated into a sort of peninsula, this part was chosen for as- cending, by means of a narrow isthmus of cinders, that connected it with the rest of the circumference of the crater.

When Capt. Tillard had ascended the ridge, it was found too narrow to walk upon, the descent within being as steep as that on the outside. But the ridge gradually wided toward the other extremity, which was elevated between twenty and thirty feet from the sea, with a ﬂat top, bounded by a precipice on one side of the channel of entrance.

Within the crater was found the skeleton of a guard-ﬁsh, so burned as to break to pieces on attempting to take it up; and it was said that great numba‘s of ﬁsh had been destroyed by the eruption, and thrown dead upon the coast of St. Michael.

The general material of which this mound consisted, was found to be a spongy substance like cinders, to which stones had been re- duced by the action of heat; but there were also other portions of stone that had undergone no such alteration.

In consequence of the supposed agreement of these three minerals, in the same primitive form of their crystals, the two latter have been arranged by the Abbé Haﬁy among those varieties of carbonate of lime which contain substances foreign to its proper chemical nature.

It has been objected to M. Hnﬁy, that the magnesian carbonate of lime, or bitter-spar, is a proper chemical compound, and as such should have a form different from that of mere carbonate of lime; and that since iron-spar frequently contains little or no lime, its crystalline form should also be different.

It is now found by the author of the present communication, that such differences as the theory appeared to require do actually exist.