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: