154 DR. DAUBENY ON THE ERUPTION OF VESUVIUS. 



It would appear that for a considerable time previous to the eruption in question, 

 the crater of the volcano had continued to throw up stones and scoriae, which falling 

 down for the most part almost perpendicularly round the point of their emission, had 

 by degrees accumulated into two conical masses, which rose up in the midst of the 

 g-reat crater. The largest of these cones is calculated to have been more than 200 

 feet in height, and possessed at one time a regular pyramidal form, with an appear- 

 ance of stability. 



It is stated, however, by Monticelli, that in May last, from the 20th of which 

 month up to the 20th of July, the volcano had continued to throw up stones and 

 ashes, and even to emit lava, both these conical hillocks were observed to be broken 

 away, and to sink towards the south ; whence, in a memoir read by him to the Aca- 

 demy of Sciences at Naples on the 5th of August, he predicted their speedy disap- 

 pearance. 



These anticipations were realized at no long period subsequently. On the 22nd 

 of August, after the volcano had continued for a month in a state of apparent repose, 

 volumes of black smoke began to show themselves on the summit of the more recent 

 of the two hillocks above noticed ; and after a smart shock of an earthquake, this 

 was succeeded by ejections of red-hot stones and scoriae, which continued to be shot 

 forth all the night with fresh quakings and rumblings of the soil. 



Early on the 23rd, a current of lava was seen to issue from the foot of the great 

 cone which encompasses the crater on its western side, and this bending in the direc- 

 tion of the point called Crocelle, reached the flanks of the rising ground denominated 

 Contaroni, whence, moving continually forwards at the rate of about six feet per 

 minute, and reinforced by a second stream of lava which had burst forth from an ad- 

 jacent point, it reached about nightfall the path generally taken from the Hermitage 

 to the summit of the mountain, which it completely blocked up. 



During the 24th, lava continued to flow from the same points, and to advance 

 down the western declivity of the mountain ; and during the night a violent shaking 

 of the volcano, which agitated the whole adjacent country, was apparently coin- 

 cident with the falling in of both the conical hillocks described as existing in the 

 interior of the crater, ho traces of which were visible in the morning. Thus we 

 have here a decided instance of two considerable pyramidal masses of volcanic ma- 

 terials, not blown into the air, as some might suppose to be the case, but actually 

 swallowed up within the cavities of the mountain in the course of a single night. 



Up to this time the western side of the volcano had been the point that yielded to 

 the internal pressure, and the inhabitants of Portici and Resina had imagined them- 

 selves to be chiefly menaced. But on the evening of the 24th a fresh vent was 

 established on the eastern side of the mountain near the Grotta del Mauro, whence 

 the lava of 1817 had issued; and after this had taken place, no more lava was ob- 

 served to flow from the western side of the cone. On the other hand, the current 

 from the eastern side was reinforced on the morning of the 25th by a second stream. 



