In considering your favour of the 16th past, I recollected my
having wrote you answers to some queries concerning the difference
between electrics _per se_, and non-electrics, and the effects of
air in electrical experiments, which, I apprehend, you may not have
received. The date I have forgotten.
We have been used to call those bodies electrics _per se_, which
would not conduct the electric fluid: We once imagined that only
such bodies contained that fluid; afterwards that they had none of
it, and only educed it from other bodies: but further experiments
shewed our mistake. It is to be found in all matter we know of; and
the distinctions of electrics _per se_, and non-electrics, should now
be dropt as improper, and that of _conductors_ and _non-conductors_
assumed in its place, as I mentioned in those answers.
I do not remember any experiment by which it appeared that high
rectified spirit will not conduct; perhaps you have made such. This
I know, that wax, rosin, brimstone, and even glass, commonly reputed
electrics _per se_, will, when in a fluid state, conduct pretty
well. Glass will do it when only red hot. So that my former position,
that only metals and water were conductors, and other bodies more or
less such, as they partook of metal or moisture, was too general.
Your conception of the electric fluid, that it is incomparably more
subtle than air, is undoubtedly just. It pervades dense matter
with the greatest ease; but it does not seem to mix or incorporate
willingly with mere air, as it does with other matter. It will not
quit common matter to join with air. Air obstructs, in some degree,
its motion. An electric atmosphere cannot be communicated at so
great a distance, through intervening air, by far, as through a
vacuum.--Who knows then, but there may be, as the ancients thought,
a region of this fire above our atmosphere, prevented by our air,
and its own too great distance for attraction, from joining our
earth? Perhaps where the atmosphere is rarest, this fluid may be
densest, and nearer the earth where the atmosphere grows denser,
this fluid may be rarer; yet some of it be low enough to attach
itself to our highest clouds, and thence they becoming electrified,
may be attracted by, and descend towards the earth, and discharge
their watry contents, together with that etherial fire. Perhaps the
_auroræ boreales_ are currents of this fluid in its own region, above
our atmosphere, becoming from their motion visible. There is no end
to conjectures. As yet we are but novices in this branch of natural
knowledge.
You mention several differences of salts in electrical experiments.
Were they all equally dry? Salt is apt to acquire moisture from a
moist air, and some sorts more than others. When perfectly dried by
lying before a fire, or on a stove, none that I have tried will
conduct any better than so much glass.
New flannel, if dry and warm, will draw the electric fluid from
non-electrics, as well as that which has been worn.
I wish you had the convenience of trying the experiments you seem to
have such expectations from, upon various kinds of spirits, salts,
earth, &c. Frequently, in a variety of experiments, though we miss
what we expected to find, yet something valuable turns out, something
surprising, and instructing, though unthought of.
I thank you for communicating the illustration of the theorem
concerning light. It is very curious. But I must own I am much in
the _dark_ about _light_. I am not satisfied with the doctrine that
supposes particles of matter called light, continually driven off
from the sun's surface, with a swiftness so prodigious! Must not
the smallest particle conceivable have, with such a motion, a force
exceeding that of a twenty-four pounder, discharged from a cannon?
Must not the Sun diminish exceedingly by such a waste of matter; and
the planets, instead of drawing nearer to him, as some have feared,
recede to greater distances through the lessened attraction. Yet
these particles, with this amazing motion, will not drive before
them, or remove, the least and lightest dust they meet with: And the
Sun, for aught we know, continues of his antient dimensions, and his
attendants move in their antient orbits.
May not all the phenomena of light be more conveniently solved, by
supposing universal space filled with a subtle elastic fluid, which,
when at rest, is not visible, but whose vibrations affect that fine
sense in the eye, as those of air do the grosser organs of the ear?
We do not, in the case of sound, imagine that any sonorous particles
are thrown off from a bell, for instance, and fly in strait lines to
the ear; why must we believe that luminous particles leave the sun
and proceed to the eye? Some diamonds, if rubbed, shine in the dark,
without losing any part of their matter. I can make an electrical
spark as big as the flame of a candle, much brighter, and, therefore,
visible further; yet this is without fuel; and, I am persuaded,
no part of the electric fluid flies off in such case to distant
places, but all goes directly, and is to be found in the place to
which I destine it. May not different degrees of the vibration of
the above-mentioned universal medium, occasion the appearances of
different colours? I think the electric fluid is always the same; yet
I find that weaker and stronger sparks differ in apparent colour,
some white, blue, purple, red; the strongest, white; weak ones red.
Thus different degrees of vibration given to the air produce the
seven, different sounds in music, analagous to the seven colours, yet
the medium, air, is the same.
If the Sun is not wasted by expence of light, I can easily conceive
that he shall otherwise always retain the same quantity of matter;
though we should suppose him made of sulphur constantly flaming. The
action of fire only _separates_ the particles of matter, it does not
_annihilate_ them. Water, by heat raised in vapour, returns to the
earth in rain; and if we could collect all the particles of burning
matter that go off in smoak, perhaps they might, with the ashes,
weigh as much as the body before it was fired: and if we could put
them into the same position with regard to each other, the mass would
be the same as before, and might be burnt over again. The chymists
have analysed sulphur, and find it composed, in certain proportions,
of oil, salt, and earth; and having, by the analysis, discovered
those proportions, they can, of those ingredients, make sulphur.
So we have only to suppose, that the parts of the Sun's sulphur,
separated by fire, rise into his atmosphere, and there being freed
from the immediate action of the fire, they collect into cloudy
masses, and growing, by degrees, too heavy to be longer supported,
they descend to the Sun, and are burnt over again. Hence the spots
appearing on his face, which are observed to diminish daily in size,
their consuming edges being of particular brightness.
It is well we are not, as poor Galileo was, subject to the
inquisition for _philosophical heresy_. My whispers against the
orthodox doctrine, in private letters, would be dangerous; but your
writing and printing would be highly criminal. As it is, you must
expect some censure, but one heretic will surely excuse another.
I am heartily glad to hear more instances of the success of the
poke-weed, in the cure of that horrible evil to the human body, a
cancer. You will deserve highly of mankind for the communication. But
I find in Boston they are at a loss to know the right plant, some
asserting it is what they call _Mechoachan_, others other things.
In one of their late papers it is publicly requested that a perfect
description may be given of the plant, its places of growth, &c. I
have mislaid the paper, or would send it to you. I thought you had
described it pretty fully[63].