**** It is perhaps not so extraordinary that unlearned men, such as
commonly compose our church vestries, should not yet be acquainted
with, and sensible of the benefits of metal conductors in averting
the stroke of lightning, and preserving our houses from its violent
effects, or that they should be still prejudiced against the use
of such conductors, when we see how long even philosophers, men
of extensive science and great ingenuity, can hold out against
the evidence of new knowledge, that does not square with their
preconceptions; and how long men can retain a practice that is
conformable to their prejudices, and expect a benefit from such
practice, though constant experience shows its inutility. A late
piece of the Abbé Nollet, printed last year in the memoirs of the
French Academy of Sciences, affords strong instances of this: for
though the very relations he gives of the effects of lightning in
several churches and other buildings show clearly, that it was
conducted from one part to another by wires, gildings, and other
pieces of metal that were _within_, or connected with the building,
yet in the same paper he objects to the providing metalline
conductors _without_ the building, as useless or dangerous.[82] He
cautions people not to ring the church bells during a thunder-storm,
lest the lightning, in its way to the earth, should be conducted down
to them by the bell ropes,[83] which are but bad conductors; and yet
is against fixing metal rods on the outside of the steeple, which
are known to be much better conductors, and which it would certainly
chuse to pass in, rather than in dry hemp. And though for a thousand
years past bells have been solemnly consecrated by the Romish
church[84], in expectation that the sound of such blessed bells would
drive away those storms, and secure our buildings from the stroke
of lightning; and during so long a period, it has not been found by
experience, that places within the reach of such blessed sound, are
safer than others where it is never heard; but that on the contrary,
the lightning seems to strike steeples of choice, and that at the
very time the bells are ringing[85]; yet still they continue to bless
the new bells, and jangle the old ones whenever it thunders.--One
would think it was now time to try some other trick;--and ours is
recommended (whatever this able philosopher may have been told to the
contrary) by more than twelve years experience, wherein, among the
great number of houses furnished with iron rods in North America, not
one so guarded has been materially hurt with lightning, and several
have been evidently preserved by their means; while a number of
houses, churches, barns, ships, &c. in different places, unprovided
with rods, have been struck and greatly damaged, demolished or burnt.
Probably the vestries of our English churches are not generally well
acquainted with these facts; otherwise, since as good protestants
they have no faith in the blessing of bells, they would be less
excusable in not providing this other security for their respective
churches, and for the good people that may happen to be assembled
in them during a tempest, especially as those buildings, from their
greater height, are more exposed to the stroke of lightning than our
common dwellings.
I have nothing new in the philosophical way to communicate to you,
except what follows. When I was last year in Germany, I met with a
singular kind of glass, being a tube about eight inches long, half an
inch in diameter, with a hollow ball of near an inch diameter at one
end, and one of an inch and half at the other, hermetically sealed,
and half filled with water.--If one end is held in the hand, and
the other a little elevated above the level, a constant succession
of large bubbles proceeds from the end in the hand to the other
end, making an appearance that puzzled me much, till I found that
the space not filled with water was also free from air, and either
filled with a subtle invisible vapour continually rising from the
water, and extremely rarefiable by the least heat at one end, and
condensable again by the least coolness at the other; or it is the
very fluid of fire itself, which parting from the hand pervades the
glass, and by its expansive force depresses the water till it can
pass between it and the glass, and escape to the other end, where it
gets through the glass again into the air. I am rather inclined to
the first opinion, but doubtful between the two. An ingenious artist
here, Mr. Nairne, mathematical instrument-maker, has made a number
of them from mine, and improved them, for his are much more sensible
than those I brought from Germany.--I bored a very small hole through
the wainscot in the seat of my window, through which a little cold
air constantly entered, while the air in the room was kept warmer
by fires daily made in it, being winter time. I placed one of his
glasses, with the elevated end against this hole; and the bubbles
from the other end, which was in a warmer situation, were continually
passing day and night, to the no small surprise of even philosophical
spectators. Each bubble discharged is larger than that from which
it proceeds, and yet that is not diminished; and by adding itself
to the bubble at the other end, that bubble is not increased, which
seems very paradoxical.--When the balls at each end are made large,
and the connecting tube very small and bent at right angles, so that
the balls, instead of being at the ends, are brought on the side of
the tube, and the tube is held so as that the balls are above it,
the water will be depressed in that which is held in the hand, and
rise in the other as a jet or fountain; when it is all in the other,
it begins to boil, as it were, by the vapour passing up through it;
and the instant it begins to boil, a sudden coldness is felt in the
ball held; a curious experiment, this, first observed and shown me by
Mr. Nairne. There is something in it similar to the old observation,
I think mentioned by Aristotle, that the bottom of a boiling pot is
not warm; and perhaps it may help to explain that fact;--if indeed it
be a fact.--When the water stands at an equal height in both these
balls, and all at rest; if you wet one of the balls by means of a
feather dipt in spirit, though that spirit is of the same temperament
as to heat and cold with the water in the glasses, yet the cold
occasioned by the evaporation of the spirit from the wetted ball will
so condense the vapour over the water contained in that ball, as that
the water of the other ball will be pressed up into it, followed by a
succession of bubbles, till the spirit is all dried away. Perhaps the
observations on these little instruments may suggest and be applied
to some beneficial uses. It has been thought, that water reduced to
vapour by heat was rarefied only fourteen thousand times, and on
this principle our engines for raising water by fire are said to be
constructed: but if the vapour so much rarefied from water is capable
of being itself still farther rarefied to a boundless degree by the
application of heat to the vessels or parts of vessels containing
the vapour (as at first it is applied to those containing the water)
perhaps a much greater power may be obtained, with little additional
expence. Possibly too, the power of easily moving water from one
end to the other of a moveable beam (suspended in the middle like a
scale-beam) by a small degree of heat, may be applied advantageously
to some other mechanical purposes.****