Mr Black on the Eruption of Mount Vesuvius. 37 



Atrio del Cavallo, and then overflowed its basin, and divided 

 into two streams; the north-western one ran through the 

 Fossa Vetrana to the villages of Massa di Somma and Sebas- 

 tiano, and overwhelmed them, and passed on towards Circola 

 and Ponticelli, and was about four miles long, and stopped 

 on Saturday the 27th. The other branch, smaller, flowed 

 down the Fossa Grande, and filled up the ravine, for about a 

 mile, in the direction of Eesina, but did not do any damage. 



Showers of Ashes. — This phenomenon was of as great im- 

 portance as that of the streams of lava, on account of the 

 darkness occasioned for several days, and submersion of the 

 country by their fall like that of snow, for several square 

 miles round Vesuvius, including Naples itself. They began 

 to fall about Friday the 26th, reached their maximum of 

 density on Sunday the 28th, and did not finally cease before 

 Friday, May 3d. 



Their composition was found to be chiefly silicates of the 

 alkalies and earths, with soluble chlorides of sodium and iron, 

 and they were collected for use as mortar for buildings, and 

 for tooth powder. 



Pillar of Cloud. — This sight was the grandest and most 

 enchanting of the phenomena of the eruption, and consisted 

 of a large cauliflower-shaped cloud of white vapour, shining 

 brilliantly white in the clear blue sky in the daytime, and 

 ilhiminated with a gorgeous red tint at night. 



Its dimensions were vast, 16,000 to 20,000 feet in height, 

 or four to five miles (as high as Gay Lussac rose in his balloon), 

 with a capping four to five miles in diameter, or twice as long 

 when floating out before the wind, the borders of which were 

 in perpetual gyration in the regions of perpetual frost. 



It began imperceptibly on Monday the 22d, reached its 

 .grandest on Friday the 26th, and Saturday the 27th, and its 

 glories finally paled as the dust clouds began to prevail 

 more and more. 



Dust Clouds. — These began after Friday the 26th, and soiled 

 and overpowered the fleecy piUar of vapour, but scarcely 

 reached haK its height, and extended themselves all over 

 the country, darkened the sky, shed down rain mixed with 

 dust, and did not end before ]May 3d. 



