ABSTRACT
For more controlled experiments on the electrical discharge we turn to Francis Hauksbee, whom we have briefly met. Hauksbee's background is rather obscure. He first attracted notice in an experimental demonstration before the Royal Society at its meeting on December 15 1703; when mercury was rushed into the evacuated glass of an pump of his, a sparkling light was given off-' a Shower of Fire descending all round the Sides of the Glasses' [3-4]. From 1704 until his final illness in 1713, he served as curator of experiments at the Society, and in November 1705 was elected Fellow for even more noteworthy
The new experiments followed two years of lackluster repetition, before the Society, of experiments by Robert Boyle and others. However, late in 1705 Hauksbee returned to his first subject, 'mercurial phosphorus' [3-5]. In this he was actually following up on earlier observations by Johann I Bernoulli, among others, that a luminosity is produced by shaking mercury in an exhausted glass vessel as in a barometer. Hauksbee's experiments in the fall of 1705 explored in greater depth the mercurial light, clearly a result of friction between mercury and glass. To ascertain whether the phenomenon was peculiar to mercury, he devised a series of experiments with various sources of frictional electricity introduced in the receiver of his pump. Beads of amber rubbed against wool cloth produced light 'without Intermission, ... discernible at three or four foot distance', while if 'the same Motion and the same Attrition was given the Amber in the Open Air, ... little did ensue, in Comparison to the Appearance of it in Vacuo' [3-6]. Replacing the beads with a small glass globe rotated swiftly by a spindle against woolen cloth 'commonly sold for Gartering' secured to a brass spring, gave better results: 'a fine Purple Light ensued, the included Apparatus being distinguishable by it' [3-7]. Even replacing the wool with 'flat shells of oysters well dry' d' produced a light 'resembling a fierce flaming Spark' [3-8]. Finally, in rubbing a glass globe against glass tubes attached to brass springs,
... a considerable Light was exhibited: The whole Included Apparatus became perfectly distinguishable it, and would have been much more so, bad not the Daylight prevented: It then being but very little after 5. P.M. a clear Horizon, and in an open Room, when the Experiment was made. [3-9] Hauksbee steadily improved his experiments, the results of which he
presented at regular intervals to the Royal Society presided over in these
yecus by Isaac l',Jewton. (Newton, keen on re-introducing the former practice of having experiments demonstrated at Society meetings, may have invited Hauksbee to the Society in the first place.) Aware that other materials might produce light when rubbed in vacuo, the glass nevertheless increasingly occupied Hauksbee's attention, and he spoke in terms of Gilbert's effluvia lodged in the glass and dislodged by rubbing.
