VOL, LVII.]j PHILOSOPHICAL TRANSACTIONS. 419 



the adjacent ground quivering like the timbers of a water-mill. Notwithstanding 

 the consistency of the lava, it ran with amazing velocity ; the first mile with a 

 rapidity equal to that of the river Severn, at the passage near Bristol. The 

 stream at its source was about 10 feet wide, but soon extended itself, and divided 

 into 3 branches, so that these rivers of fire communicating their heat to the 

 cinders of former lavas, between one branch and the other, had the appearance 

 at night of a continued sheet of fire, 4 miles in length, and in some parts near 

 2 in breadth. Your lordship may imagine the glorious appearance of this un- 

 common scene, such as passes all description. The lava, after having run pure 

 for about 100 yards, began to collect cinders, stones, &c. and a scum was thus 

 formed on its surface, which in the day-time had the appearance of the river 

 Thames," after a hard frost and great fall of snow, when beginning to thaw, car- 

 rying down vast masses of snow and ice. In two places the liquid lava totally 

 disappeared, and ran in a subterraneous passage for some paces, then came out 

 again pure, having left the scum behind. In this manner it advanced to the cul- 

 tivated parts of the mountain, destroying the cottages in its way. The lava, at 

 the farthest extremity from its source, did not appear liquid, but like a heap of 

 red hot coals forming a wall, in some places 10 or 12 feet high, which rolling 

 from the top soon formed another wall, and so on, advancing slowly, not more 

 than about 30 feet in an hour. 



The mouth of the volcano has not thrown up any large stones since the 2d 

 eruption of lava, on the 10th of April, but has thrown up quantities of small 

 ashes and pumice stones, that have greatly damaged the neighbouring vineyards. 

 In his last visit to Mount Vesuvius the 3d of June, he still found that the lava 

 continued, but the rivers were become rivulets and had lost much of their ra- 

 pidity. 



Mount Etna in Sicily broke out the 27th of April, and made a lava in two 

 branches, at least 6 miles in length, and a mile in breadth, and that of Vesu- 

 vius resembled it in every respect, except that mount Etna, at the place whence 

 the lava flowed (which was 12 miles from the mouth of the volcano), threw up 

 a fountain of liquid inflamed matter to a considerable height ; which he was told, 

 mount Vesuvius has done in former eruptions. Other particulars of this, and 

 some later eruptions of these two mountains, may be seen with advantage, in 

 Sir W.'s observations on these volcanos, as extracted from these Transactions, 

 and published with notes in 1772. 



XXI. Observations on the Heat of the Waters at Bath. By John Howard, Esq.. 



F.R.S. p. 201. 



King's batii pump 1 13° Hot bath, coolest part 96° 



Hot bath pump 114 Ditto, warmest part gj 



Cro»8 bath pump 108 The pump in the hot bath 1 IS 



3 H 2 



