622 PHILOSOPHICAL TRANSACTIONS. [aNNO 1780. 



and other volcanic matter during this last eruption, that it was supposed 

 to be raised 250 feet or more. Three such eruptions as the last would com- 

 pletely fill up the valley, and, by uniting Vesuvius and Somma, form them into 

 one mountain, as they most probably were before the great eruption in the reign 

 of Titus. In short, the whole face of Vesuvius was changed. Those curious 

 channels, in which the lava ran in the preceding month of May, were all 

 buried. The volcano appeared to have also increased in height; the forn^ of the 

 crater was changed, a great piece of its rim towards Somma being wanting; and 

 on the side towards the sea it was also broken. There were some very large 

 cracks towards the point of the cone of the volcano, which made it probable, that 

 more of the borders of the crater would fall in. The ridge of fresh volcanic 

 matter on the cone of Vesuvius towards Somma, and the thick stratum in the 

 valley, were likewise full of cracks, from which there issued a constant sul- 

 phureous smoke that tinged them and the circumjacent scoriae and cinders with 

 a deep yellow, or sometimes a white tint. 



The number and size of the stones, or, more properly speaking, of the frag- 

 ments of lava, which were thrown out of the volcano in the course of this erup- 

 tion, and which lay scattered thick on the cone of Vesuvius, and at the foot of 

 it, were incredible. The largest they measured was in circumference no less than 

 108 English feet, and 17 feet high. It was a solid block, and much vitrified: 

 in some parts of it there were large pieces of pure glass, of a brown yellow 

 colour, like that of which common bottles are made, and, throughout, its pores 

 seemed to be filled with perfect vitrifications of the same sort. The spot where 

 it fell, was plainly marked by a deep impression, almost at the foot of the cone 

 of the volcano, and it took 3 bounds before it settled, as was plainly perceived by 

 the marks it has left on the ground, and by the stones which it pounded to atoms 

 under a prodigious weight. Another solid block of ancient lava, 66 feet in 

 circumference, and 1 9 feet high, being nearly of a spherical shape, was thrown 

 out at the same time, and lay near the former. This stone had the marks 

 of having been rounded, nay almost polished, by continual rolling in torrents, 

 or on the sea-shore; but it had undoubtedly been, in that state, thrown out of 

 the volcano, and may therefore be the subject of curious speculations. Another 

 block of solid lava that was thrown much farther, and which lay in the valley 

 . between the cone of Vesuvius and the Hermitage, was l6 feet high, and Q2 in 

 circumference, though it appeared, by the large fragments that lay round, and 

 were detached from it by the shock of its fall, that it must have been twice as 

 considerable when in the air. There were thousands of very large fragments of 

 different species of ancient and modern lavas, that lay scattered on the cone of 

 Vesuvius, and in the vallies at its foot; but these 3 were the largest of those they 

 measured. They measured two other atones in the valley between Somma and 



