144 Professor Silliman's Geological Notes. 



It is perhaps too much to infer from these casual observa- 

 tions so wide a deduction as that all the travertine is due 

 to this origin from sulphur waters charged with bicarbonate 

 of lime; but it is not going further than is allowed by a 

 prudent philosophy, to say that travertine is now forming on 

 the shores of Lake Solfaterra from this cause. 



3. 'Present Condition of Vesuvius. 



The eruption of Vesuvius in February 1850, and that of 

 the year previous, entirely changed the summit features of 

 this ancient mountain of fire. The former crater disappeared, 

 being filled with scoria and ashes, while two craters now 

 occupy the summit of the cone. The deepest and most active 

 of these is that of February 1850, which is situate on the 

 side of the cone nearest to Pompeii. It is somewhat lower, 

 and has a much greater depth than its immediate neighbour, 

 which is on the side of the bay of Naples. We had no means 

 of measuring its depth accurately, but judging from the time 

 required for the returning sound of a stone cast into its 

 mouth, as well as from inspection and comparison, we as- 

 sumed the depth of the new crater to be from 800 to 1000 

 feet. It is acutely funnel-shaped at an angle of not less than 

 60". It is impossible, because of the stream and vapour of 

 sulphurous acid, to see its bottom, even if not prevented by 

 the danger of the descent to a position where one might 

 hope to catch a glimpse of its bottom. Its activity at present 

 is confined to the emission of vapour, and even this seems at 

 times, when viewed from the sea, to be wanting. On the 

 summit, however, these vapours appear dense enough, and 

 are sufi&cient to prevent the possibility of making the entire 

 circuit of the crater. From this cause we were unable to 

 examine the lip dividing the crater of 1850 from its neigh- 

 bour. The observer is much struck, not only with the change 

 of form in the summit, as shewn by the drawings of Pro- 

 fessor Scacchi, but also with the sharpness of the lip of both 

 craters, which is such that it is hardly possible for more 

 than two persons to stand abreast upon it. During the late 

 eruption, the lava found vent from the base of the cone on a 

 level with the sand plain which fills the ancient crater of 



