Royal Society (Great Britain).

The Philosophical transactions of the Royal society of London, from their commencement in 1665, in the year 1800 (Volume 8) online

. (page 41 of 85)
Online LibraryRoyal Society (Great Britain)The Philosophical transactions of the Royal society of London, from their commencement in 1665, in the year 1800 (Volume 8) → online text (page 41 of 85)
Font size
QR-code for this ebook


ticles to touch at their point of breaking equilibrium, you must open them so
much on the contrary side, that the spring will be bent far beyond any uses in-
tended to be made of it, as appears by fig. 17, where two particles are brought
to touch at the equilibrating point e; and by fig. 18, where many particles
being put into that condition, the spring is brought round quite into a
circle.

Now the common practice in making springs, is the most likely to produce
this effect required in the particles; for the hard spring, whose particles were
round,, or nearly so, is heated anew, and while cooling gently, the mutual
attraction increases tlie contact, so that the particles grow flatter in those places
where before they had but a small contact; and lest this contact should become
too great, the spring's softening is stopped by quenching it in water, or oil,
or grease. Another way of making springs, is to begin and shape them in
cold unelastic steel, and then having heated them to a small degree, for ex-
ample, to a blood red heat, immediately to cool them in some proper liquors.
This also settles the particles in their oblong figure, through which they must
pass before they become round, or nearly so, in a white heat. That particles
of steel are fixed in the figures which they have at the instant of dipping, will
not appear strange, when we consider, that dipping red-hot steel in cold
liquors, in a particular position, makes it magnetical. If it be asked, how we
account for making springs only with hammering, it is easily answered, that
we can make iron and steel magnetical only with hammering; and if we can
give and destroy poles in the whole piece, there is no improbability to think

VOL. Vlll. Y Y



34(j I'HILOSOPHICAL TRANSACTIONS. [aNNO 1739.

we can give poles to little parts ; or rather bring into a particular situation the
poles which they have; for if the poles that we have considered be placed
quite irregularly, there will be no elasticity at all. Agreeably to this, springs
may be made of other metals than iron or steel, though not so perfect, by
hammering ; for it will be sufficient for the little particles to have poles that
attract and repel one another, driven by the hammering into a regular order.

This, applied to the vibration of a string, will better solve its several cases,
than attraction alone; and the elasticity of glass is just the same as that of a
very brittle steel -spring.

Some Thoughts and Experiments concerning Electricity. By J, T. Desagu-
liers, LL. D. F. R. S. N° 454, p. 186.

The phaenomena of electricity are so odd, that though we have a great
many experiments on that subject; we have pot yet been able from their com-
parison to settle such a theory, as to lead us to the cause of that property of
bodies, or even to judge of all its effects, or find out what useful influence
electricity has in nature : though certainly, from what we have seen of it, we
may conjecture, that it must be of great use, because it is so extensive.

Though some persons have been too hasty in their conjectures, and too apt
to run into hypotheses not sufficiently supported by experiments; yet it would
be of great use to settle some general propositions concerning electricity, from
the light we have already, and what we may further discover by future experi-
ments ; provided we have a sufficient number of them to settle a general rule.
For example ; I now propose some general assertions to be considered, and to
be rejected or allowed of, as a number of experiments shall determine; but to
stand only as queries till they are settled.

I have hitherto avoided entertaining the Society on this subject, or pursuing
it so far as I might have done, considering that I can excite as strong an elec-
tricity in glass, by rubbing it with my hand, as any body can, because I was
unwilling to interfere with the late Mr. Stephen Gray, who had wholly turned
his thoughts that way ; but was disposed to decline it entirely, if he imagined
that any thing was done in opposition to him. But now I intend not only to
go on myself in making electrical experiments, but shall always be ready to
make such as shall be proposed by any member of the Society. The Queries
which I have already examined, are the following :

Query 1 . Whether all bodies in general are not capable of receiving the
electricity which has been given to a tube by friction, though there be a great
many bodies, such as metals and vegetables, &c. in which we have not hitherto



VOL. XL!.] PHILOSOPHICAL TRANSACTIONS. 347

been able to excite any electricity by heat, or friction, or any other operation
on the bodies themselves ?

Query 1. Whether, when a string is stretched out at length, with a body
hanging at one end of it, to which body we would communicate the electricity
of the tube rubbed at the other end, the supporters of the string ought not to
be of such bodies as are capable of having electricity excited in them, by fric-
tion, heating, beating, or patting, or some immediate operation on the bodies
themselves ?

Query 3. Whether these supporters of the string, mentioned in the last
Query, which stops the electrical virtue from passing any further, are not of
such a kind, as are incapable of having the electrical virtue excited in them
immediately by any operation yet known ; though they are all capable of re-
ceiving it from a rubbed tube, even at a great distance, by the communication
of a string made of vegetable substances ?

Query 4. Whether the reason, that some supporters transmit the electricity
running from the rubbed tube along the string, to bodies beyond them, be not
as follows, viz. that having received some of the electrical stream, they soon
become saturated with it, and so receiving no more of it, let the rest pass on
without disturbing it?

Query 5. Whether the reason, that supporters made of vegetable substances,
metals, and such others, as stop the electricity abovementioned from running
any farther along the string than the place where it rests upon them, be not
this ? viz. that they are never saturated with the electrical stream, but conti-
nually receive it, and transmit it to the next contiguous body, provided that
contiguous body be of the same kind with themselves, and also contiguous to
other bodies of the same sort : I mean such as would stop the electricity, if
the string was supported by them. For even these supporters will transmit
the electricity, if terminated at each end by bodies that transmit the electricity,
when they support the string.

Query 6. Whether we may not distinguish all bodies in general, in respect
of electricity, into such as may be excited to electricity, and such as cannot
be excited to electricity ? the two kinds of bodies receiving the electricity from
other bodies into which it has been excited differently ; the first also trans-
mitting the electricity, while the others do not.

These queries are such as arise from a consideration of experiments made by
others, and such as I have made myself.

Experiments relating to the first Query. — I stretched a cat-gut, about 5
feet in length, and fastened it to the top of two chairs in a horizontal situa-
tion ; and such another cat-gut string to two other chairs parallel to the first,

Y Y 2



348 PHILOSOPHICAL TRANSACTIONS. [aNNO IJSft.

;ind at the distance of 15 or 20 feet from the former. I then suspended one
end of a packthread to the middle of the first cat-gut, and carried it on so as
to lay it over the middle of the other cat-gut, and leave the other end of the
packthread hanging down about a foot below the cat-gut, with a loop to hang
several bodies to it, successively to receive the electricity excited by the tube
and applied to the other end of the packthread.

All the bodies I tried received the electricity communicated from the rubbed
tube along the string, which appeared by holding a thread fastened to a stick,
the thread being attracted towards the suspended body.

1. A gold medal. 2. A silver medal. 3. A copper medal. 4. A brass ball.
5. A steel ball. 6. A tin ball. 7. A leaden ball. 8. Sulphur, g. Sealing-
wax. 10. Pumice stone. 11. Bees-wax. 12. Resin. 13. Sal ammoniac.
14. Ivory. 15. Human bone. l6. Fish-skin. IJ. Loadstone. 18. P'lesh.
19. Cotton. 20. Wax-candle. 21. Tallow-candle. 22. A leek. 23. Celeri.
24. Tobacco-pipe. 25. A glass^ball. 26. A rush rolled up.

Experiments relating to Query 2, — Retaining the first supporting string of
cat-gut, instead of the last cat-gut supporter, I made the packthread pass over
t-he following substances successively, all which transmitted the electricity to
the body suspended at the end of the packthread; viz. 1. A silk string,
2. Hair rope. 3. Parchment. 4. A thong of sheep-skin, but it stopped the
electricity till it was dry and warm. 5. A list of woollen cloth. 6. A list of
flannel. 7- Cadis, or a kind of worsted tape. 8. Quills. 9. Whalebone.
10. A man's thigh-bone. U. A bladder. 12. A cat, held between two.
13. A tallow-candle. 14. A wax-candle (the string was also laid over the
unburned cotton wick at the end of the candle). 15. A tallow-candle and its
wick. 16. Tobacco-pipe, with a cat-gut or a packthread through it, or with-
out, that is, a packthread string being fastened at each end of it. 1 7. A
sword-belt. 18. A piece of a white hat. 19. A piece of a black hat. 20. A
glass tube. 21. The same with water in it. 22. With spirit of wine. 23. The
same with mercury in it. 24. Sealing-wax. 25. Crape.

All these substances, except the sheep-skin, the tobacco-pipe, the quills, the
candles, and the bone, not only transmitted the electricity, but became so far
electrical, as to attract the thread a little way on each side of the supported
packthread. More experiments are required to be made, before this query can
be turned into an assertion.

Experiments relating to Query 3. — Instead of the last supporter of cat-gut,
near the suspended body, I made use of the following substances, stretched
from chair to chair : and then the thread hanging on the stick was not at all



VOL. XLI.] PHILOSOPHICAL TRAWSACTIONS. 349

attracted by tlie suspended ivory ball, which I made use of in all the experi-
ments to try the supporters,

1. A hempen rope. '2. A small packthread. 3. A drawn sword. 4. A
sword in the scabbard, 5. The scabbard without the sword. 6. A twisted
cotton thread. 7. I'ape made of thread. 8. Bars, tubes and wires of copper,
brass, iron and lead. g. White paper and brown. 10. A moist thong of
sheep-skin. 11. Celeri. 12. Leeks. 13. Fir-wood. 14. A cane. 15. A
piece of black thorn. 1 6. The same rushes that had before received the elec-
tricity when suspended. 17. A sponge dry. 18. White thread, ip. Hay.
20. A marble slab.

Such bodies as were too short to reach from chair to chair, were lengthened
out by pieces of packthread at each end.

Experiments relating to Query 4. — The cat-gut supporters, and all the others
mentioned in the experiments to Query 3, which transmitted the electricity,
attracted the thread of the stick near the conducting packthread, but not so
far as the chairs to which the said supporters were fastened.

Experiments relating to Query 5. — All the supporters which did not transmit
the electricity, when they reached from chair to chair, were made to transmit,
when they were lengthened out with cat-gut at each end, and then they be-
came electrical themselves from one end to the other, as becoming part of the
suspended body ; and becoming so saturated, as not to be able to carry the
electricity on either side any farther than the cat-gut to which they were fas-
tened.

Experiments relating to Query 6. — ^The late Mr. Stephen Gray has, by rub-
bing, excited electricity in several of those bodies, which I have made sup-
porters of, to transmit the electricity. See Philos. Trans. N° 366. I have
done the same with several others, but not with all of them, though I shall
try them all : but as it is more difficult to excite that virtue in some than
others ; and all the experiments in general succeed better in dry and cold
weather, than in moist and warm, I must wait for proper opportunities to make
the experiments, and then I shall communicate them.

Experiments concerning mixed Substances. — I . Cadis, or woollen tape, laid on
thread-tape, when made a..supporter, transmitted the electricity. 2. When the
thread-tape was uppermost, the electricity was stopped. 3. When they were
twisted together, the electricity was transmitted, but most weakly when the
packthread going to the ball was laid over that part of the twist which had the
thread-tape.

The two paper supporters, which did not transmit the electricity, ought to
have done it according to Query 2; because, by Mr. Gray's experiments, elec«



350 PHILOSOPHICAL TRANSACTIONS. [aNNO 1739-

tricity is to be excited in the paper by rubbing: therefore, perhaps the papers
wanted to be drier or warmer, so that I shall try them again. These are the
only two experiments that do not agree with the 2d Query ; but I would not
omit mentioning them, because it is the part of an impartial philosopher, to
mention as well those things which favour, as those that disagree with his
hypotheses and conjectures.

Experiments made before the Royal Society, Feb. 2, 1737-8. By J. T. Desa-
guliers, LL.D. F.R.S. N° 454, p. igS.

In the following account, which is the sequel of former experiments, I call
conductors those strings, to one end of which the rubbed tube is applied; and
supporters such horizontal bodies as the conductor rests on.

Exper. 1. — Old packthread supporters transmitted electricity but weakly,
though more strongly when twisted with cat-gut; but new packthread did
better.

N. B. Where it is not mentioned otherwise, an ivory ball hangs at the end
of the conductor; and its electricity is tried by a thread applied near it.

Exper. 1. A conducting string of cat-gut received the electricity a little
way ; but did not carry it quite to the tube.

Exper. 3. — Two conducting strings, one of cat-gut, and one of pack-
thread, compared, the first attracted less and less, as the distance from the
tube increased; and the other more and more; till it was strongest at the sus-
pended body: but both ceased immediately after the removal of the tube.

Exper. 4. — A sealing wax supporter transmitted the electricity, but received
little or none when suspended. If it was but just rubbed with the hand, it
attracted the thread when first suspended; and strongly, if much rubbed; but
that virtue was soon lost, if the tube was applied to the conducting string, and
then it would receive no more electricity from the tube. If the stick of wax
was wet, then it would strongly receive the electricity.

A wax supporter wet, and silk string wet, did not transmit the electricity.

Exper. 5. — Dried ox-guts did not transmit electricity when held in hand; but
when tied to cat-gut, transmitted it ; and, when suspended, received it plen-
tifully.

Exper. 6. — The same with a small cord.

Exper. 7. — The same with a rod of iron, and tube of brass.

Exper. 8. — A glass tube, made conductor, received the electricity but a
little way.



VOL. XLI.j PHILOSOPHICAL TKANSACTIONS. 351

Ea-per. Q. — Dry sheep- skin transmitted the electricity, but not wlien wet,
though it received it then, when suspended.

Exper. 10. — A middle supporter of packthread was again supported on one
side by a glass tube, and on the other by sealing-wax, and had at each end an
ivory ball hanging. Those balls became electrical in the same manner, and at
same time, as the ball at the end of the conducting spring.

Exper. 1 1. — When a bar of oak was made use of instead of the tube, or a
small iron bar instead of the wax, the electricity was stopped : but when the bar
was thrust a little way into a glass tube, the electricity was communicated as
before.

Experiment made at the Royal Society, Feb. Q, 1737-8. By the Same.

N°454, p. 196.

I fixed 6 iron radii, of twisted iron wire, to a brass ring, of 2 feet diameter,
and half an inch wide, which had a socket in the centre, by which to set it either
on an upright glass tube, or on a wooden pillar : then were hung on the end
of the 6 radii, next to the circumference, the following substances. 1. A piece
of resin. 2. A stick of wax. 3. An apple. 4. An ivory ball. 5. A steel ball.
6. A glass ball.

Exper. 1 and 2. — I rubbed the tube, and applied it to the centre of this
machine, as it stood on a glass tube ; and the electricity was communicated to
all the suspended bodies, and the ring also ; but none of them received it, when
the machine stood on a wooden pillar, with its foot on the floor.

Exper. 3. — I tied to the ends of the 6 radii as many cat-gut strings, but
so long as to unite together about a foot higher than the centre of the ring,
where they were suspended by another cat-gut string 3 feet in length, the top
of which was fastened to a hempen rope. Then applying the rubbed tube very
near the place where all the cat-gut strings joined over the ring, at which ring
the same bodies were suspended as before, neither the bodies nor ring re-
ceived any electricity.

Note. This was done in foul weather, when the electricity does not extend it-
self far from the tube : but in fair weather, the electrical virtue, at the same
distance, reached the iron radii of the ring ; and consequently the ring and
bodies suspended, though the virtue was not propagated, along the cat-gut :
for if the tube was applied a little higher to the single cat-gut, so as the
effluvia, or virtue darted directly from the tube, did not reach the ring, or its
iron radii, then no virtue was communicated to the ring nor to the suspended
bodies, &c.



354 PHILOSOPHICAL TRANSACTIONS. [aNWO 173Q.

Exper. 4. — I suspended the ring by 6 packthreads, just in the same man-
ner as the cat-gut strings before ; but still all those strings were suspended by
the perpendicular cat-gut of 3 feet in length. Then all the bodies received
the electricity from the rubbed tube applied to the top of the pyramid of pack-
thread.

Exper. 5. — Instead of the perpendicular cat-gut, between the pyramid of
packthread and the upper hempen string, I substituted a packthread ; and then
no virtue was communicated to the ring, but all went up the hempen string,
and was lost ; except when the tube was held very near the ring, and then
it gave a small degree of electrical attraction to the ring, and the bodies sus-
pended at it.

Exper. 6. — Having again suspended the ring with the bodies and pyramid
of packthreads to the perpendicular cat-gut, I tied a packthread to the ring,
and carried it horizontally about 20 feet from the ring; and having fastened
to it a cat-gut string, 3 feet long, I gave it an assistant to hold : then applying
the rubbed tube to the end joining that cat-gut, the electricity was commu-
nicated to the ring, and all the suspended bodies, as appeared by applying the
white thread near them, which was attracted by every part of the ring, and all
the bodies.

Experiments made before the Royal Society, Feb. l6, 1737-8. By the Same.

N°454, p. 198.

Exper. \ . — I applied the rubbed tube to a burning candle, and it had no
manner of effect on the flame ; but as soon as the candle was blown out, it
attracted the smoke at 4 or 5 inches distance.

Exper. 1. — A horizontal packthread, of about 18 feet in length, being ter-
minated by the cat-gut strings, of 3 feet long each, and hung, towards one
of the ends of the packthread, on it a candlestick with a lighted candle in it ;
then applying the rubbed tube to the other end of the packthread, the candle-
stick attracted the thread, and it was also attracted by the candle, but not
within 2 or 3 inches of the flame ; but as soon as the candle was blown out,
the thread was attracted by every part of it ; nay, even the wick, when it was
quite extinguished.

Exper. 3. — I suspended a wax candle in the same manner, and the experi-
ment succeeded the same ; only the electricity came not so near the flame in
the wax as in the tallow candle.

Exper. 4. — I hung an iron wire, \6 feet long, horizontally by two cat-gut
strings at its ends, about 3 feet long each, and bent down the wire from the



VOL. XLI.] I'HILOSOPHICAL TRANSACTIONS. 353

place joined to the cat-gut, so as to hang down a foot at one end ; then ap-
plying the rubbed tube at the other end, this conductor carried the electricity
along to the ball ; but not so well as the packthread conductor ; but it did some-
thing better when it was wet.

The same happened when the conductor was brass wire of the same length.

The packthread conductor also carried the effluvia stronger when wet.

An Account of some Electrical Experiments made before the Royal Society on
Thursday the \6th February, 1737-8. By the Same. N° 454, p. 200.

Exper. 1. — I took the glass tube ab of two inches diameter, fig. l, plate 8,
which had at one end a, a brass ferril with a brim cemented to it, and at the
other end b, a brass cap close at top, the brass-work being joined to it, in
order to exhaust it of its air on occasion. When this tube was very dry it
would become electrical by rubbing, so as to snap by passing the ends of the
fingers near it ; but that virtue could not be excited in the tube nearer the
brass at the ends than from a to b, and not unless the tube was very dry
within.

The tube being thus prepared, and having an ivory ball c of about 2 inches
diameter, tied to it at the end b by a short string, I passed the tube through
the horizontally suspended place dd, till it was stopped by the brim at a ; and
as il hung perpendicularly, the ball c was within a foot and a half of the floor.
The plate dd was about 10 inches in diameter, and suspended by 3 small cat-
gut strings, as e e, of about 2 feet in length, all which were tied together at
B, to a hempen string hanging from the cieling at p.

By reason of the distance of the ends of the cat-gut strings close to the plate
ateee, I was able to thrust in between them one end of an open tube gg,
after it had been rubbed so as to make it electricul, to see whether I could
make the aforesaid suspended tube ab the conductor of electricity to the ball c;
but the first trial was in vain.

Exper. 2. Then laying horizontally over the plate dd an iron bar, a quarter
of an inch thick, and a yard long, I hung at the ends of it two ivory balls c, c,
of the same size as c, by packthreads of the same length at the tube ab.

Having again made the tube gg electrical, I applied it over a, as before, and
immediately the two balls c, c, received the electricity, so as to attract the
thread of trial t, hanging at the end of the stick sx, when applied near
them ; though it received no motion when applied to c. But if the strings
H c, instead of packthread, were cat-gut, then the balls c, c, received no
electricity from the tube gg, rubbed and applied over a

VOL. VIII. Z z



354 VHILOSOPHICAL TRANSACTIONS. [aNNO 1739.

To be certain that the rubbed tube is made electrical, I pass my fingers near
it after rubbing, to hear- whether it snaps ; but always rub again before I apply
it ; because by snapping it loses its electricity at the place where it snaps.

Exper. 3. — When I rubbed the tube ab, it would then attract the thread
of trial T between a and b ; but not at all above a or below b, unless when I
applied the tube gg above a : then the thread of trial would be attracted by
the plate dd, and the top of the great tube from a to a, but no lower. It
would also be attracted by all the bar hh, and only 3 or 4 inches below h.

Exper. 4. — Having filled the tub ab with water, the electricity of the rubbed
tube GG, applied at a, ran strongly down the tube ab, and impregnated the ball
c, so as to make it strongly attract the thread of trial, while the balls c, c, re-
ceived no virtue at all. But on wetting the cat-gut strings h, c, with a sponge,
all the 3 balls c, c, c, strongly received the electrical virtue.

Exper, 5. — I took away the bar hh, and its balls and strings ; and having
well dried the tube, I rubbed it, and hung it up as before ; so that it would
snap, or attract the thread from a to b, but no where else.

Then putting the small bar hh into the middle of the tube ab, in its axis,
represented by the pricked line, on application of the rubbed tube gg at a, the
virtue was immediately communicated to the ball c. The same thing happened
when instead of the bar, a brass wire, a walking cane, a small green stick, or
small packthread, was placed in the axis of the tube.

Exper. 6. — 1 took a barometer tube, empty, and very dry, and placed it in



Online LibraryRoyal Society (Great Britain)The Philosophical transactions of the Royal society of London, from their commencement in 1665, in the year 1800 (Volume 8) → online text (page 41 of 85)