184 



battery ; the whole being properly connected with an exceedingly de- 

 licate galvanometer. On making the apparatus revolve rapidly, not 

 the slightest deflection of the needle was perceptible. Hence, if so 

 large a surface of hot water be incapable of conducting as much elec- 

 tricity as would agitate the most delicate astatic needle, though the 

 exciting cause was sufficient to make a wire revolve round a magnet, 

 and overcome the resistance of the mercury through which it was 

 dragged, it would require an enormous power of this kind to decom- 

 pose water. The author, therefore, considers it unlikely that electri- 

 city induced by magnets will ever supply the place of the voltaic bat- 

 tery in effecting chemical decomposition ; and he concludes by ob- 

 serving, that " as no increase of electro-magnetic power is gained by 

 increasing the decomposing powers of a battery, and as action and re- 

 action are equal, it appears improbable that we shall ever obtain high 

 decomposing powers by any increase in magneto-electric induction." 



A paper was then read, entitled, "Notice of the Remains of the 

 recent Volcano in the Mediterranean." By John Davy, M.D. F.R.S. 

 Assistant Inspector of Army Hospitals. 



The author communicates an account given by Captain Swinburne, 

 dated the 24th of August, of a dangerous shoal, in latitude 37° 9' N. 

 and longitude 12° 43' E, consisting principally of black sand and 

 stones, with a circular patch of rock, which has been left by the vol- 

 cano that lately appeared in the Mediterranean. Captain Swinburne 

 furnished the author with two specimens of the air which was seen 

 rising from the site of the volcano, in small silver threads of bubbles. 

 These were found, upon examination by chemical tests, to consist of 

 between 9 and 10 parts of oxygenous to 79 or 80 of azotic gases. 



The author adduces arguments in favour of the supposition that this 

 air is disengaged from sea water at the bottom in contact with the 

 loose and probably hot ashes and cinders composing the shoal, rather 

 than that it arises from the extinct volcano. He is also disposed to 

 extend this theory to the explanation of the gases disengaged from 

 hot springs, which are generally found to consist of a mixture of oxy- 

 genous and azotic gases, the former being in less proportion than in 

 atmospheric air, in consequence of its abstraction by oxidating pro- 

 cesses from the air originally contained in these waters. 



The Society then adjourned over the Easter vacation, to meet again 

 on the 18th of April. 



April 18, 1833. 



FRANCIS BAILY, Esq., Vice-President, in the Chair. 



Thomas Botfield, Esq. ; Sir William Burnett, Knt. K.C.H. ; Major 

 F. H. Shadwell Clerke, K.H. ; Robert Adam Dundas,Esq. ; the Rev. 

 Augustus Page Saunders, M.A. ; and Thomas Stephens Davies, Esq., 

 were elected Fellows of the Society. 



A paper was read, entitled, Cl On Improvements in the Instruments 



