Even
before
his experiments in drawing off the electric charge with points
led to some practical suggestions which resulted in the invention
of the lightning-rod. In the letter of July, 1750, which he wrote
on the subject, he gave careful instructions as to the way in
which
these rods might be constructed. In part
"May not the knowledge of this power of points b 16416g611q e of use to
mankind in preserving houses, churches, ships, etc., from the
stroke of lightning by directing us to fix on the highest parts
of the edifices upright rods of iron made sharp as a needle, and
gilt to prevent rusting, and from the foot of these rods a wire
down the outside of the building into the grounds, or down round
one of the shrouds of a ship and down her side till it reaches
the water? Would not these pointed rods probably draw the
electrical fire silently out of a cloud before it came nigh
enough to strike, and thereby secure us from that most sudden and
terrible mischief?
"To determine this question, whether the clouds that contain the
lightning are electrified or not, I propose an experiment to be
tried where it may be done conveniently. On the top of some high
tower or steeple, place a kind of sentry-box, big enough to
contain a man and an electrical stand. From the middle of the
stand let an iron rod rise and pass, bending out of the door, and
then upright twenty or thirty feet, pointed very sharp at the
end. If the electrical stand be kept clean and dry, a man
standing on it when such clouds are passing low might be
electrified and afford sparks, the rod drawing fire to him from a
cloud. If any danger to the man be apprehended (though I think
there would be none), let him stand on the floor of his box and
now and then bring near to the rod the loop of a wire that has
one end fastened to the leads, he holding it by a wax handle; so
the sparks, if the rod is electrified, will strike from the rod
to the wire and not effect him."[4]
Not satisfied with all the evidence that he had collected
pointing to the identity of lightning and electricity, he adds
one more striking and very suggestive piece of evidence.
Lightning was known sometimes to strike persons blind without
killing them. In experimenting on pigeons and pullets with his
electrical
machine,
outright, was sometimes rendered blind. The report of these
experiments were incorporated in this famous letter of the
The attitude of the Royal Society towards this clearly stated
letter, with its useful suggestions, must always remain as a blot
on the record of this usually very receptive and liberal-minded
body. Far from publishing it or receiving it at all, they derided
the whole matter as too visionary for discussion by the society.
How was it possible that any great scientific discovery could be
made by a self-educated colonial newspaper editor, who knew
nothing of European science except by hearsay, when all the great
scientific minds of Europe had failed to make the discovery? How
indeed! And yet it would seem that if any of the influential
members of the learned society had taken the trouble to read over
Franklin's clearly stated letter, they could hardly have failed
to see that his suggestions were worthy of consideration. But at
all events, whether they did or did not matters little. The fact
remains that they refused to consider the paper seriously at the
time; and later on, when its true value became known, were
obliged to acknowledge their error by a tardy report on the
already well-known document.
But if English scientists were cold in their reception of
Franklin's theory and suggestions, the French scientists were
not. Buffon, perceiving at once the importance of some of
Franklin's experiments, took steps to have the famous letter
translated into French, and soon not only the savants, but
members of the court and the king himself were intensely
interested. Two scientists, De Lor and D'Alibard, undertook to
test the truth of Franklin's suggestions as to pointed rods
"drawing off lightning." In a garden near Paris, the latter
erected a pointed iron rod fifty feet high and an inch in
diameter. As no thunder-clouds appeared for several days, a guard
was stationed, armed with an insulated brass wire, who was
directed to test the iron rods with it in case a storm came on
during D'Alibard's absence. The storm did come on, and the guard,
not waiting for his employer's arrival, seized the wire and
touched the rod. Instantly there was a report. Sparks flew and
the guard received such a shock that he thought his time had
come. Believing from his outcry that he was mortally hurt, his
friends rushed for a spiritual adviser, who came running through
rain and hail to administer the last rites; but when he found the
guard still alive and uninjured, he turned his visit to account
by testing the rod himself several times, and later writing a
report of his experiments to M. d'Alibard. This scientist at once
reported the affair to the French Academy, remarking that
"Franklin's idea was no longer a conjecture, but a reality."
|
