Scientific Intelligence. — Geology. 197 



published in the Philosophical Transactions for 1812, the au- 

 thor offered it as a conjecture, that the metals of the alkalies 

 and earths might exist in the interior of the globe; and, on be- 

 ing exposed to the action of air and water, give rise to volcanic 

 fires, and to the production of lavas, by the slow cooling of 

 which, basaltic and other crystalline rocks might subsequently 

 be formed. Vesuvius, from local circumstances, presents pecu- 

 liar advantages for investigating the truth of this hypothesis; 

 and of these the author availed himself during his residence at 

 Naples, in the months of December 1819, and of January and 

 February 1820. A small eruption had taken place a few days 

 before he visited that mountain, and a stream of lava was then 

 flowing, with considerable activity, from an aperture in the 

 mountain a little below the crater, which was throwing up 

 showers of red hot stones every two or three minutes. On its 

 issuing from the mountains it was perfectly fluid, and nearly 

 white hot ; its surface appeared to be in violent agitation from 

 the bursting of numerous bubbles, which emitted clouds of 

 white smoke. There was no appearance of vivid ignition in the 

 lava when it was raised, and poured out by an iron ladle. A 

 portion was thrown into a glass bottle, which was then closed 

 with a ground stopper, and, on examining the air in the bottle 

 some time afterwards, it was found not to have lost any of its 

 oxygen. Nitre thrown upon the surface of the lava did not 

 produce such an increase of ignition, as would have attended the 

 presence of combustible matter. The gas disengaged from the 

 lava proved, on examination, to be common air. When the 

 white vapours were condensed on a cold tin plate, the deposit 

 was found to consist of very pure common salt ; and the va- 

 pours themselves contained nine per cent, of oxygen, the rest 

 being azote, without any notable proportion of carbonic acid or 

 sulphurous acid gases; although the fumes of the latter of these 

 gases were exceedingly pungent in the smoke from the crater of 

 the volcano. On another occasion, the author examined the sa- 

 line incrustrations in the rocks near the ancient bocca of Vesu- 

 vius ; and found them to consist principally of common salt, 

 with some chloride of iron^ — a little sulphate of soda, — and a 

 still smaller quantity of sulphate or muriate of potassa, with a 

 minute portion of oxide of copper. In one instance, in which 



