[ 229 ]
bursting off from the lower part of the spindle the stones contiguous to it on that side.
At each of the angles of the metal, the stone on which it rested is cracked, which probably was occasioned by the lightning issuing with greater freedom from those parts, than from the flat surface.
No part of the spindle is in the least injured by the lightning, notwithstanding the great quantity which, from it’s effects, appears to have been accumulated in it [1].
From hence, as low as to the corniche B, it seems to have been conducted along the surface of the spire, which was wetted by the rain that had fallen in the morning, before the lightning: and having been accumulated in the iron bars B and C, in discharging itself from them, it has made the greatest explosion at this place.
Under this part the freedom of it’s passage seems to have been hindered by all the dry stonework underneath, which was defended from the rain by the corniches: and it appears from some experiments which I formerly made[2], that dry free stone, when warm'd to a certain degree (which probably does not exceed the heat which the stones of buildings acquire in hot weather) resists the passage of the electric fluid or lightning so strongly, that with plates of that stone, instead of glass, I performed the Leyden experiment.
- ↑ In the year 1750 the stones surrounding this spindle were so much damaged, that there was a necessity of taking them down and rebuilding that part of the spire. The cause of this was not known at that time, it is probable that it was occasioned in the same manner as the present accident.
- ↑ Philosophical Transactions, anno 1759. p. 83.
