THE Fire of Electricity (as I have before observed) is extremely
delicate, and sets on Fire, as far as I have yet experienced, only
inflammable Vapours. Nor is this Flame at all heightned by being
superinduced upon an Iron Rod, red hot with coarser culinary Fire, as in
a preceeding Experiment; nor diminished by being directed upon cold
Water. However I was desirous of knowing, if this Flame would be
effected by a still greater Degree of Cold; and in order to determine
this, I made an artificial Cold; by which the Mercury, in a very nice
Thermometer adjusted to _Fahrenheit_'s Scale, was depressed in about 4
Minutes from 15 Degrees above the freezing Point to 30 Degrees below it,
that is, the Mercury fell 45 Degrees. From this cold Mixture, when
electrified, the Flashes were as powerful and the Stroke as smart as
from the red hot Iron. I could have made the Cold more intense, but the
above was sufficient for my Purpose. This Experiment seems to indicate,
that the Fire of Electricity is affected neither by the Presence or
Absence of other Fire. For as red hot Iron, by Sir _Isaac Newton_'s
Scale of Heat, is fixed at 192 Degrees, and as the Ratio between Sir
_Isaac_'s Degrees and _Fahrenheit_'s is as 34 to 180, it necessarily
follows, that the Difference of Heat between the hot Iron and the cold
Mixture is 1040 Degrees; and nevertheless this vast Difference makes no
Alteration in the Appearance of the electrical Flame. We find likewise,
that as the Fire, arising from the Refraction of the Rays of Light by a
_Lens_, and brought to a _Focus_, is observed first at some small
Distance from their Surfaces, to set on Fire combustible Substances; the
same Effect, as I have before observ'd, is produced in like Manner by
electrical Flame.
I MAY perhaps be thought too minute in some of the before-mentioned
Particulars; but in Inquiries abstruse as these are, where we have so
little _a priori_ to direct us, the greatest Attention must be had to
every Circumstance, if we are truly desirous of investigating the Laws
of this surprizing Power. For, as has been said upon another Occasion by
my ever honoured Friend MARTIN FOLKES, Esq; our most worthy President,
"that Electricity seems to furnish an inexhaustible Fund for Inquiry;
and sure Phænomena so various and so wonderful can arise only from
Causes very general and extensive, and such as must have been designed
by the Almighty Author of Nature for the Production of very great
Effects, and such as are of great Moment to the System of the Universe."
IF these Observations receive the Countenance of this learned Society, I
shall think myself sufficiently recompensed, and am,
_Gentlemen, with the highest Esteem,_
_your most Obedient_
_humble Servant_,
W. WATSON.
_FINIS._
-----
Footnote 1:
Dr. _Gowin Knight_, F. R. S.
Footnote 2:
I call _Electrics per se_ or originally-_electrics_, those Bodies, in
which an attractive Power towards light Substances is easily excited
by Friction; such as Glass, Amber, Sulphur, Sealing-wax, and most dry
Parts of Animals, as Silk, Hair, and such like. I call _Non-electrics_
or Conductors of Electricity, those Bodies, in which the above
Property is not at all or very slightly perceptible; such as Wood,
Animals living or dead, Metals and vegetable Substances. See _Gray_,
_Du Fay_, _Desaguliers_, _Wheler_, in the Philosophical Transactions.
Footnote 3:
Page 6.
Footnote 4:
I have constantly observed, that the electrical Attraction through
Glass is much more powerful, when the Glass is made warm, than when
cold. This Effect may proceed from a two-fold Cause: First, warm Glass
does not condense the Water from the Air, which makes the Glass, as
has been before[5] demonstrated, a Conductor of Electricity: secondly;
As heat enlarges the Dimensions of all known Bodies, and consequently
causes their constituent Parts to recede from each other, the
electrical Effluvia, passing in straight Lines, find probably a more
ready Passage through their Pores.
Footnote 5:
Page 13.
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Transcriber's note:
All footnotes moved to the end of the text.
Page 5, 'Contract' changed to 'Contact,' "the Contact of
Non-electrics..."
Page 6, 'Power' changed to 'Poker,' "I suspended a Poker in silk
Lines;"