334 Improved Method of Constructing 
any coincident occurrence which could produce these changes ; 
so that perhaps it may be in vain, without further experiments, 
to attempt any rational explanation of the phenomena. Would 
it be fair to suppose, that the black fumes may be in a negative 
state, and that the white fumes, consisting principally of aque- 
ous vapour, sulphuric and muriatic acids, and sulphur, may, 
when these vapours become condensed, (as in Volta’s artificial 
experiment), and when the sulphur sublimes in the air, be 
brought into a positive istate, and that these two states of the 
black and white fumes may sometimes act separately upon the 
electrometer; or sometimes wholly, and sometimes partially, 
neutralize each other, either by induction or position, or by a 
discharge from one to the other? In violent eruptions, no 
doubt, the frequent flashes of lightning which are seen to take 
place amongst the clouds of smoke and vapours proceeding 
from the crater, are occasioned by such discharges. 
The thermometer in the shade, on the mountain, on the 4th 
July, at 8 o’clock A.M., stood at 76°, and in the sun, witha . 
blackened ball, at 83°. At the same hour at Naples it stood 
at 78° in the shade, and at 100° inthe sun, with a black ball. 
The magnetic needle on the mountain never exhibited, with 
me, any such extraordinary signs of oscillation, as it appears to 
have done with Spallanzani; neither could M. Gimbernat, 
Councillor of State to the King of Prussia, (who witnessed 
some of my experiments on Vesuvius,) ever perceive any such 
effects, although he frequently tried the experiment. M. Gim- 
bernat is the gentleman to whom visitors to Vesuvius are so 
much indebted for the luxury of fine pure water in this region 
of heat, thirst, and fatigue, by the establishment of an apparatus 
for condensing the water of the aqueous fumerole. 
Art. 1X. On an Improved Method of Constructing the 
Dead Escapement for Clocks. By B. L. Vuiuiamy, 
Clock-maker to the King. 
[Communicated by the Author.] 
The dead escapement originally invented by G. Graham, 
F.R.S., being perhaps practically the best clock escapement 
