[ 49 I 
would be affected by a ftill greater Degree of Cold j 
and in order to determine this, I made an artificial 
Cold 5 by which the Mercury, in a very nice Ther- 
mometer adjufted to Fahrenheit's Scale, was depreffed 
in about 4 Minutes, from 15 Degrees above the 
freezing Point to 30 Degrees below it 5 that is, the 
Mercury fell 45 Degrees. From this coid Mixture, 
when electrified, the Flafhes were as powerful, and 
the Stroke as (mart, as from the red hot Iron. I 
could have made the Coid more intenfe, but the 
above was fufficient for my Purpofe. This Experi- 
ment feems to indicate, that the Fire of Electricity 
is affected neither by the Prefence or Abfence of 
other Fire. For as red hot Iron, by Sir Ifaac New- 
tons Scale of Hear, is fixed at 192 Degrees, and 
as the Ratio between Sir Ifaacs Degrees and 
Fahrenheifs is as 34 to 180, it neceffariiy follows, 
that the Difference of Heat between the hot Iron 
and the cold Mixture is 1040 Degrees; and never- 
thelefs this vaft Difference makes no Alteration in 
the Appearance of the electrical Flame. We find 
likewife, that as the Fire, ariling from the Refrac- 
tion of the Rays of Light by a Lens y and brought 
to a Focus , is obferved, firft, at fame fmall Diftance 
from their Surfaces, to fet on Fire combuftible Sub- 
fiances ; the fame Effect, as I have before obferv'd, 
is produced in like manner by electrical Flame. 
I may perhaps be thought too minute in fome of 
the before-mentioned Particulars; but, in Inquiries 
abftrufe as thefe are, where we have fo little ^ priori 
to direct us, the greateft Attention muft be had to 
every Circumftance, if we are truly defirous of in- 
G veftigating 
