Sir H. Davy on Electrical Phenomena in Vacuo. 
cuum was not solely owing to a smaller quantity of electricity 
passing through it; for the same discharge which produced a 
faint light in the upper part of the tube, produced a 
bright purple light in the lower part, and a strong spark in the 
atmosphere. 
In order to try the effects of other vapours. Sir Humphry 
formed a vacuum with pure olive oil^ whose boiling point is not 
much below that of mercury, and also with the butter^ or chloride 
of cmtimony^ whose boiling point is about S88® of Fahrenheit. 
The electricity which passed through the vapour of the chloride 
was much more brilliant than when it passed through the vapour 
of the oil, and more brilliant through the vapour of the oil than 
through the vapour of the mercury, at common temperatures. 
The light was purely white in the vapour of the chloride^ and 
red, approaching to purple, in that of the oil; and, in both 
cases, a permanent elastic fluid was produced by its transmis- 
sion. 
Considering the diminution of the density of vapours, by di- 
minution of temperature, as in a geometrical progression, while 
the decrements of temperature are in an arithmetical progres- 
sion (a law which appears to be established by the experiments 
both of Mr Dalton and of Sir Humphry Davy), and considering 
the boiling points of 
Mercury, 
oa, 
Chloride of Antimony, 
Tin, 
as at 600® of Fahrenheit. 
540 
340 
5000 
all above 52°, and taking the elastic force of the vapour of water 
at this temperature, to be such as to balance about 45 parts of 
an inch of mercury ; Sir Humphry Davy finds that the relative 
strength of vapour will be, for mercury, 000015615 ; for olive 
oil, 0016819; for chloride of antimony, 01692; and for tin, 
37015, preceded by 48 cyphers. 
Sir H. Davy next endeavoured to ascertain if the power of 
the Toricellian vacuum %o transmit electricity, was diminished by 
a diminution of temperature. This appeared to be the case to 
about 20° above zero ; but between -[- 20° and — 20°, the lowest 
temperature that he could produce by pounded ice apd muriate 
of lime, it seemed stationary. The light was in this case 
VOL. VII. NO. 14, OCT. 1822. a 
