95 



water taken from the crater appeared to consist of sea-water holding 

 in suspension a fine dust, together with filaments resembling vege- 

 table fibres, which the author supposes to have been derived from 

 sea-weed drawn into the water. The saline ingredients of this water 

 differed from that of the Mediterranean, chiefly in containing more 

 sulphate of lime, and a little alumina, oxide of iron, and a trace of 

 oxide of manganese ; all these in combination with an acid, probably 

 the sulphuric or muriatic, and a notable portion of hypersulphite of 

 lime and magnesia. He could not detect in it any free acid or alkali, 

 or the presence, even in combination, of any potash or ammonia, or 

 nitric acid, nor the slightest trace of bromine or iodine. The gas 

 emitted by the volcano appeared, as far as could be determined from 

 an examination of two specimens, to consist chiefly of carbonic acid, 

 with a trace of sulphuretted hydrogen. 



The author observes in conclusion, that the results of his inquiry 

 are almost entirely of a negative kind ; and in this respect correspond 

 with those obtained by Sir Humphry Davy, with respect to Vesuvius, 

 and which are describedinhispaper "On thePhaenomenaof Volcanos," 

 published in the Philosophical Transactions for 1828. They accord- 

 ingly tend to corroborate the simple hypothesis there adopted in ex- 

 planation of the phaenomena of volcanic action ; namely, that of the 

 existence of an ignited nucleus of fluid matter, occasionally forced 

 through the cooled crust of the earth by the expansive power of steam 

 and gas : and they militate strongly against the hypothesis of the che- 

 mical origin of volcanos, and of their being attended by a decompo- 

 sition of water by the metallic bases of the earths and alkalies. 



A drawing of the volcano in its active state of eruption accom- 

 panied the paper, together with a plan and views of the island. 



January 12, 1832. 

 JOHN BOSTOCK, M.D., Vice-President, in the Chair. 



The Bakerian Lecture for 1832, entitled "Experimental Re- 

 searches in Electricity — Second Series," by Michael Faraday, Esq. 

 F.R.S., was read. 



The success of the author in exhibiting the evolution of elec- 

 tricity by induction from ordinary magnets, led him to conclude 

 that similar effects might be obtained from the magnetism of the 

 earth, and even to an extent that might render it available in the 

 construction of new electrical machines. These expectations have 

 been fully realized; and the researches which establish the in- 

 fluence of terrestrial induction in giving rise to electrical currents, 

 form the subject of this second paper. 



Whenever a hollow helix, the terminal wires of which were con- 

 nected with those of a galvanometer, and which inclosed a cylinder 

 of soft iron, was held with its axis in the line of the magnetic dip, 

 and suddenly inverted, the evolution of electric currents was imme- 

 diately rendered sensible by the deflection of the needle of the gal- 

 vanometer ; a deflection in the contrary direction being produced 

 the moment the helix was again inverted, so as to recover its first 



