36 Proceedings of the Boy at Physical Society. 



enough, into the water accounted at once for its bad qualities^ 

 and the results of my analysis, although it is quite possible 

 that if it had been tested by the other process I have indicated, 

 it would have been in all probability reported as being excel- 

 lent water. 



II. — Notice of an Account of the Great Eruption of Mount 

 Vesuvius, of April 1872. By W. T. Black, Esq. 



Mr W. T. Black contributed a communication of an account 

 of the great eruption of Vesuvius of April 26th, 1872, compiled 

 from the journal of his brother, then staying at ISTajDles, and 

 from information collected from letters in the journals of the 

 time. 



It was illustrated by numerous photographs and views 

 obtained by his brother, and by a collection of volcanic 

 minerals, by charts and diagrams of the mountain, drafted 

 from original sources, showing the course of the streams of 

 lava, the formation of the crater, and the structure of the 

 pillar of cloud. 



This eruption is called a paroxysmal one, in contradis- 

 tinction to ordinary ones, because it was accompanied by all 

 the three physical manifestations, viz., by the piUar of cloud, 

 the showers of ashes, and the streams of lava, with their con- 

 comitant phenomena. 



Ordinary eruptions, on the other hand, may have only the 

 steam cloud, and this may have either ash showers with it 

 alone, or lava streams alone coincident with it. 



Date and Duration. — The eruption began on Tuesday, April 

 23d, 1872, reached its climax on Friday the 26th, and ceased 

 about Thursday, May 2d, thus lasting about a week. 



Lava Streams. — These began to flow from the top of the 

 cone on Tuesday the 23d, and did not cease before Saturday 

 27th. There were two great streams of lava that flowed 

 down from the cone ; one smaller on the south side towards 

 Camaldoli, about two miles long, which did not cause much 

 mischief to life or property. The larger one, on the north 

 side, flowed out of the great fissure of the cone, filled up the 



