You desire my opinion of Pere Beccaria's Italian book[68]. I have
read it with much pleasure, and think it one of the best pieces on
the subject that I have seen in any language. Yet as to the article
of water-spouts, I am not at present of his sentiments; though I must
own with you, that he has handled it very ingeniously. Mr. Collinson
has my opinion of whirlwinds and water-spouts at large, written some
time since. I know not whether they will be published; if not, I
will get them transcribed for your perusal[69]. It does not appear
to me that Pere Beccaria doubts of the _absolute impermeability
of glass_ in the sense I meant it; for the instances he gives of
holes made through glass by the electric stroke are such as we have
all experienced, and only show that the electric fluid could not
pass without making a hole. In the same manner we say, glass is
impermeable to water, and yet a stream from a fire-engine will force
through the strongest panes of a window. As to the effect of points
in drawing the electric matter from clouds, and thereby securing
buildings, &c. which, you say, he seems to doubt, I must own I think
he only speaks modestly and judiciously. I find I have been but
partly understood in that matter. I have mentioned it in several of
my letters, and except once, always in the _alternative, viz_. that
pointed rods erected on buildings, and communicating with the moist
earth, would either _prevent_ a stroke, _or_, if not prevented, would
_conduct_ it, so as that the building should suffer no damage. Yet
whenever my opinion is examined in Europe, nothing is considered but
the probability of those rods _preventing_ a stroke or explosion,
which is only a _part_ of the use I proposed for them; and the
other part, their conducting a stroke, which they may happen not to
prevent, seems to be totally forgotten, though of equal importance
and advantage.
I thank you for communicating M. de Buffon's relation of the effect
of lightning at Dijon, on the 7th of June last. In return, give me
leave to relate an instance I lately saw of the same kind. Being in
the town of Newbury in New England, in November last, I was shewn
the effect of lightning on their church, which had been struck a
few months before. The steeple was a square tower of wood, reaching
seventy feet up from the ground to the place where the bell hung,
over which rose a taper spire, of wood likewise, reaching seventy
feet higher, to the vane of the weather-cock. Near the bell was fixed
an iron hammer to strike the hours; and from the tail of the hammer
a wire went down through a small gimlet-hole in the floor that the
bell stood upon, and through a second floor in like manner; then
horizontally under and near the plaistered cieling of that second
floor, till it came near a plaistered wall; then down by the side of
that wall to a clock, which stood about twenty feet below the bell.
The wire was not bigger than a common knitting-needle. The spire was
split all to pieces by the lightning, and the parts flung in all
directions over the square in which the church stood, so that nothing
remained above the bell.
The lightning passed between the hammer and the clock in the
above-mentioned wire, without hurting either of the floors, or
having any effect upon them (except making the gimlet-holes, through
which the wire passed, a little bigger,) and without hurting the
plaistered wall, or any part of the building, so far as the aforesaid
wire and the pendulum wire of the clock extended; which latter
wire was about the thickness of a goose-quill. From the end of the
pendulum, down quite to the ground, the building was exceedingly
rent and damaged, and some stones in the foundation-wall torn out,
and thrown to the distance of twenty or thirty feet. No part of the
afore-mentioned long small wire, between the clock and the hammer,
could be found, except about two inches that hung to the tail of
the hammer, and about as much that was fastened to the clock; the
rest being exploded, and its particles dissipated in smoke and air,
as gunpowder is by common fire, and had only left a black smutty
track on the plaistering, three or four inches broad, darkest in
the middle, and fainter toward the edges, all along the cieling,
under which it passed, and down the wall. These were the effects and
appearances; on which I would only make the few following remarks,
viz.
1. That lightning, in its passage through a building, will leave wood
to pass as far as it can in metal, and not enter the wood again till
the conductor of metal ceases.
And the same I have observed in other instances, as to walls of brick
or stone.
2. The quantity of lightning that passed through this steeple must
have been very great, by its effects on the lofty spire above the
bell, and on the square tower all below the end of the clock pendulum.
3. Great as this quantity was, it was conducted by a small wire and
a clock pendulum, without the least damage to the building so far as
they extended.
4. The pendulum rod being of a sufficient thickness, conducted the
lightning without damage to itself; but the small wire was utterly
destroyed.
5. Though the small wire was itself destroyed, yet it had conducted
the lightning with safety to the building.
6. And from the whole it seems probable, that if even such a small
wire had been extended from the spindle of the vane to the earth,
before the storm, no damage would have been done to the steeple by
that stroke of lightning, though the wire itself had been destroyed.