Omnipotens sempiterne Deus, &c. ... ut ante sonitum ejus effugentur ignita jacula inimici, percussio fulminum, impetus lapidum, læsio tempestatum, &c.
[85] En 1718. M. Deslandes fit savoir à l'Academie Royale des sciences, que la nuit du 14 ou 15 d'Avril de la mème année, le tonnerre étoit tombé sur vingtquatre églises, dequis Landernau jusqu'à Saint-Pol-de-Léon en Bretagne; que ces églises étoient précisément celles où l'on sonnoit, & que la foudre avoit épargné celles ou l'on ne sonnoit pas: que dans celle de Gouisnon, qui fut entièrement ruinée, le tonnerre tua deux personnes de quatre qui sonnoient, &c. Hist. du l'Ac. R. des Sci. 1719.
[Experiments, Observations, and Facts, tending to support the Opinion of the Utility of long pointed Rods, for securing Buildings from Damage by Strokes of Lightning.]
Read at the Committee appointed to consider the erecting Conductors to secure the Magazines at Purfleet, Aug. 27, 1772.
EXPERIMENT I.
The prime conductor of an electric machine, A. B. ([See Plate IV].) being supported about 10 inches and a half above the table by a wax-stand, and under it erected a pointed wire 7 inches and a half high, and one-fifth of an inch thick, and tapering to a sharp point, and communicating with the table; when the point (being uppermost) is covered by the end of a finger, the conductor may be full charged, and the electrometer c[86], will rise to the height indicating a full charge: but the moment the point is uncovered, the ball of the electrometer drops, showing the prime conductor to be instantly discharged and nearly emptied of its electricity. Turn the wire its blunt end upwards (which represents an unpointed bar) and no such effect follows, the electrometer remaining at its usual height when the prime conductor is charged.
Vol. I. page 388.
Plate IV.
