372 Geological Society, 



that the chemical theory of the origin of volcanoes is still to be 

 maintained, as being more philosophical and more consistent with 

 facts and experiments, tlian the hypothesis of a central ignited fluid, 

 which has been, from time to time, mechanically forced up to the 

 surface of the earth. 



Whilst on volcanic ground, I must remark, that the records of 

 the past year have been impressively marked by the appearance and 

 disappearance of an island in the Mediterranean, which, notwith- 

 standing its ephemeral existence, fortunately engaged so large a 

 share of scientific attention, as to have afforded some important data 

 for the explanation of geological phenomena. In these inquiries cur 

 countrvmen at Malta, appear to have been most active. Sir William 

 Hotham, the Admiral commanding on that station, directed un- 

 remitting observations to be made, from the first appearance of this 

 islet above the sea, when visited by Captain Swinburne, to its com- 

 pletion and passage into a quiescent state, when examined and accu- 

 rately suvveved by Captain Wodehouse : and, fortunately for science, 

 the latter officer was accompanied by a distinguished chemist, 

 who has been the first to furnish his countrymen with a good 

 account of the volcano. Although this able memoir of Dr. Davy 

 has been read before the Royal Society, and will shortly be given 

 to the public, I may here be permitted to state, that a careful ex- 

 amination of all the products of this eruption, both solid and 

 gaseous, has convinced the author that of all the hypotheses of vol- 

 canic action, that which was last adopted by his great and lamented 

 brother, and which refers such paroxysmal elevations to the expansive 

 power of steam and gas, generated within the earth by the percola- 

 tion of water upon an ignited nucleus, is the most easily reconcilable 

 with the phaenomena observed upon this spot. We also learn from Dr. 

 Davy that, besides the scoria and cinders of which this island was 

 chiefly constituted, various fragments of dolomitic limestone and sand- 

 stone, similar to those forming the nucleus of the adjacent island of 

 Sicily, were brought up in the ejections ; and it is further important 

 for geologists to know, that from the accurate surveys of sub- 

 marine levels in these seas, previously made by Captain Smyth, 

 R.N., as well as from more recent soundings, this island was 

 elevated from beneath a deep sea, and not upon the site of a 

 pre-existing reef of rocks, as had been asserted. Whilst oir 

 countrymen were visiting this island, the fortunate proximity of 

 M. Hoffmann on the adjoining coast of Sicily, enabled this merito- 

 rious Prussian geologist to visit it on two occasions ; and an 

 abridged account of his observations has been transmitted to us 

 by our Vice-President Mr. Horner, and read before the Society. 

 At a later period the French Government sent out M. Constant 

 Prevost, an observer well known for the accuracy of his researches and 

 the ingenuity of his speculations ; and we are therefore entitled to hope, 

 that his detailed accounts will throw much additional light on the re- 

 lations of this new-born island, to many volcanic pha;nomena of more 

 ancient date. The examination of M. Hoftmann has, indeed, already 

 proved of singular interest, in showing that this eruption occurred 

 on a line which has been subject to volcanic action from remote an- 

 tiquity, 



