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

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xjase separated much further, and kept their repulsive force much longer.

Exper. 7. Mr. W. hung up two fragments of barometer tubes, each about
a foot long, by blue silk lines going through them, so that they hung parallel,
horizontal, at equal heights, and about one quarter of an inch asunder ; on
holding the excited tube above and under them, they manifestly receded from
each other.

He suspended the same fragments of tubes by blue silk lines of equal length,
from a cross blue silk in a perpendicular position, each having a little red seal-
ing wax at the upper end, to hinder the strings from slipping off. The excited
tube being brought near them, they receded manifestly, especially at the lower
ends ; the distance from one another, when at rest, being about a quarter of
an inch.

Carol. I . From the repulsive state of the pendulous threads, tied transversely
with two or more threads, and bending out from each other, where at liberty,
it follows that all the threads of a table-cloth, or other large piece of linen,
when made electrical, have a tendency to fly from each other : and conse-
quently, were the repulsive force strong enough, the whole would be dissolved,
or torn in pieces. A short thread of black silk, by repeated applications of the
tube, has separated into its smallest fibres. Whence is suggested more plainly,
than from any other known experiment, a reason for the dissolution of bodies
in their respective menstruums, viz. that the particles of the solvend having im-
bibed the particles of the menstruum, so as to be saturated with them, the
saturated particles become repulsive of each other, separate, and the mass flies
to pieces.

And hence perhaps arises a reason, why particles of bodies specifically heavier
than the menstruums in which they are dissolved, are, after the dissolution and
dispersion, suspended all over the menstruum, viz. that they repel each other.
Attraction is insufficient; for parts attracted equally in all directions, are, in effect,
not attracted at all; and the imperfection of the fluid will not do; for if this oc-
casioned the suspension, striking or shaking the vessel would make them subside.

Carol. 2. Hence we plainly see how heat may divide the particles of water with
greater or less force, in proportion to the degree of saturation, and throw them
into the air ; where they may continue to ascend, if at the same time they are
divided, they are expanded into little shells or bubbles, of a diameter large
enough to be specifically lighter than the lower air, as Dr. Halley has saga-
ciously conjectured. Or if the upper parts of the air, as being less saturated than



312 PHILOSOPHICAL TRANSACTIONS. [aNNO iJSQ.

the lower parts, may be able to draw them upwards, till the excess of weight,
which is constantly increasing, is equal to the excess of attraction.
Prop. III. Bodies, made Electrical by rubbing, do themselves repel one another,
or the electrical excited Bodies themselves repel one another.

Exper. 1 . The two fragments of tubes before mentioned, prop. 2, exper. 8,
being suspended horizontally, and in a position parallel to each other, Mr. W.
held in one hand, and with the other rubbed some time ; then gently letting
them go so as to be at rest, they receded from each other towards that end
which had not been taken hold of.

Also, he suspended a single little tube, about a foot long, by a long blue silk
line, perpendicularly, and on a table placed the great tube fixed in a stand as
before, and excited each alternately, 2 or 3 times ; then gently moved the tube
with the stand it was fixed in, near the suspended little one : the little tube ma-
nifestly receded so much, that a cross blue silk line, stretched horizontally at
about an inch distance on the opposite side, would sometimes, on the tirst ap-
proach of the great tube, be touched by it.

Exper. 2. Three scarlet silks, each pendulous by loops from a cross silk
line, and close together, being rubbed downwards two or three times, between
the finger and thumb, showed a considerable repulsive force with regard to each
other, forming themselves immediately into a triangular pyramid, and conti-
nuing in this state of separation some time ; and, which shows their attraction
at the same time, with regard to other bodies not excited, coming to them
when brought near them.

He observed the same repulsive force in 3 yellow and 3 green silks, under the
same circumstances, and excited in the same manner, but not in so great a de-
gree as in scarlet. In blue the repulsive force was scarcely discernible after seve-
ral times rubbing.

Scholium. Dr. Hales, in the 12th article of his 13th experiment, in the 2d
volume of his Statical Essays, observes, " That if a piece of one of the bronchiae
or gills of the muscle shell -fish, be cut off, and put into a small concave glass,
with three or four drops of its liquor, and be then placed under a double mi-
croscope, the blood may be seen greatly agitated in the fine vessels ; and at the
cut edge of the piece of gill, may with great pleasure be seen many blood-glo-
bules, repelled from the cut orifices of the blood vessels, and attracted by other
adjoining vessels : also other globules rolling round their centre, and repelling
each other ; whence (as he says) it is plain, that bodies, by brisk rubbing and
twirling about, may acquire, in a watry fluid, both attractive and repulsive virtue
or electricity."



VOL. XLI.] PHILOSOPHICAL TRANS ACTIOKS. 313

From our last experiments, we are led to think, that the globules of the
blood, if by friction they acquire an electrical attractive virtue, must of neces-
sity repel one another ; and that electricity is not so properly called an attractive
and repulsive virtue, as a virtue attractive of those bodies that are not attractive
themselves, and repulsive of those that are ; and that this repulsive force of the
electrical blood-globules, excited by friction, as they flow in their channels (and
particularly in the small ones, and perhaps more so in those of the lungs, where
the refrigerating power of the air may assist, as Dr. Hales has observed) ; this
repulsive force of the blood-globules, may be the great cause that hinders the
blood from coagulating as it circulates ; may be the great cause of the constant
perspiration in a healthy state, and of the increase of it, caeteris paribus, in pro-
portion as the velocity and friction of the blood increases.

If these things are so, the necessity of exercise appears more plainly than ever,
in order to keep the body in a healthy state, as we may observe here the very
steps that nature makes use of to free herself from her suppressions.

^n Account of some of the Electrical Experiments made hy Granvile JVheler,
Esq. at the Royal Society s house, on May 11, 1737. By C. Mortimer^
M.D. R.S. Seer. N°453, p. 112.

Exper. 1 . — A large octavo book was placed horizontally on silk lines, and
the upper surface strewed with several pieces of leaf brass, all or the greater
part of which flew upwards, from one another, and off the book, on holding an
excited tube at a little distance underneath the book.

Exper. 1. — Two lines were extended horizontally the whole length of the
library, being between 30 and 40 feet, distant from one another about 2 feet
at one end, and meeting together in a knot at their other ends, the whole
lines being packthread, except 5 feet of silk line tied at each of the separated
extremities, as well as at the knot where the other ends united, in order to
stop the current of the effluvia. On the united extremities was placed hori-
zontally a piece of card about 2 inches square, on which were strewed pieces of
leaf brass. The excited tube being held at a little distance under the separated
extremities of the packthread, the leaf brass on the card at the other end flew
upwards, and off the card.

Exper. 3. — Five glass receivers, placed one within another, on an electrical
cement of bees-wax and Venice turpentine, were all exhausted. In the inner-
most a fine white thread, about 5 inches long, was suspended from the crown
of it, by means of a little cement made of bees- wax and oil. " On moving the
excited tube up and down near the side of, and horizontally to and from the

VOL. VIII. S s



314 rHILOSOPHlCAL TRANSACTIONS. [aNNO 173Q.

outer receiver, the suspended thread manifestly made many vibrations corres-
ponding to the motions of the tube.

Exper. A. — An electrical circular cake of bees- wax and rosin, 10 inches in
diameter, was placed horizontally on a tall glass receiver, near 3 feet high,
such as is made use of for dropping the feather and guinea. This cake being
the preceding evening about 8 o'clock, warmed with a hot iron held over it, and
then struck perpendicularly all over its surface with the hands in parallel direc-
tions, and so left covered with a thin pasteboard, was about 1 1 o'clock next
day at noon gently uncovered, and an ivory ball, about one inch and half di-
ameter, placed in the centre, a fine white thread about ten inches long, with a
small piece of cork, the size of a pin's head, at the end of it, being held be-
tween the finger and thumb, was gently let down on the vertex of the ball ; it
first flew off at some distance, and then made several pretty regular revolutions
from west to east about it, in the form of a circle.

Exper. 5. — The ball was removed, and the cake again warmed and excited
as before ; after which the ball was replaced at a little distance from the centre,
nearer to Mr. Wheler ; the consequence of which was, that the pendulous
little body moved with a direct motion as before, but in an orbit that resembled
an ellipse, having the ball in one of its foci.

Exper. 6. — Two bullets fixed on little stands of cork, about one quarter of an
inch high, were placed on the cake, each about an inch distant from its centre,
and in a line with the centre and Mr. Wheler ; the pendulous body described an
orbit resembling an ellipse, having the two bullets for its foci, and the motion
was direct from west to east.

Exper. 7. — Instead of the cork, another pendulous body of a cylindrical form
was made use of, tied to a fine white thread, about 20 inches long ; the cylin-
der consisted of two circular bases of paper, half an inch diameter, but all cut
away except a ring and a small bar across the middle, through which basis 6
equal fine threads passed at equal distances from one another, knotted at the
lower base separately, and joined together in one knot at about half an inch
distance from the upper base, from which knot proceeded the long thread.
This body moved from west to east about the central ball, and at the same time
discovered a motion about its own axis in the SHnie direction ; but after 2 or 3
turns generally stopped, and turned the contrary way, which seemed to arise
from the untwisting of the thread.

Exper. 8. — A thread about a foot long, was suspended from a horizontal line
of packthread, aod parallel to it an excited tube placed erect in a stand, the
thread approached the tube, and continued in a state of attraction. A thread of



VOL. XL!.] PHILOSOPHICAL TRANSACTIONS. 315

the same length, suspended from a silk line, vibrated backward and forward 2
or 3 times, being first attracted, and then repelled, and continuing some time
repelled; but on joining the top of the tube, by a packthread going round it,
to the loop of the thread, the thread continued constantly in a state of repul-
sion, showing no tendency to attraction.

Exper. g. — Two black silks, about the same length with the thread in the
preceding experiment, were suspended by loops from a horizontal red silk line,
at the distance of about half an inch from each other ; on holding the excited
tube under them, the silks swelled out from one another, and then jumped
away on each hand to the distance of 1 feet.

Exper. 10. — A circular board of nearly the same diameter with the electric
cake, was suspended horizontally by 6 silk lines, tied to one silk line which was
brought over a pulley at the top of a frame of wood, so as to be moved up and
down. From the board hung 6 fine white threads, about 18 inches long, fixed
by a little cement at equal distances from each other. The board being let
down till the ends of the threads were about an inch distant from the electric
cake, which was directly under, and had the ivory ball on its centre ; the
threads all approached towards the centre of the cake, both when the ball was
in the centre, and when taken away, keeping an equal distance from the centre,
and from one another, as long as a packthread joined the circle of board and the
frame to keep it steady ; and on removing the ball out of the centre, towards
the circumference, the figure lengthened, the threads next the ball advancing
nearer the circumference ; when the ball was placed at about an inch distance
from the circumference, the thread that was before nearest the circumference
whipped between the ball and the centre, so as to be almost in the same plane
with its two neighbouring threads, the figure formed by the extremities re-
sembling an ellipse with one end cut off. But when, instead of the packthread
that joined the board to the frame, a blue silk line was tied in the same manner
in all respects, the threads, instead of coming towards the centre, all flew away
at a great distance from the cake, and from one another.

It ought to be observed in the experiments of the circular motion of the pen-
dulous body, that Mr. Wheler's hand seemed as steady as possible, except in
the first experiment, when a little trembling appeared; Mr. George Graham
taking a very good method to observe it, by keeping his eye fixed on a point at
a considerable distance, in the same line with the end of Mr. Wheler's finger
and his own eye.

Yet when Mr. Wheler had finished the experiments to the satisfaction of all
present, Mr. Hawskbee, Mr. George Graham, and Dr. Mortimer, held the
thread with the pendulous body over the cake with the ball on its centre, after

s s 2



3l6 PHILOSOPHICAL TRANSACTIONS. [aNNO \7'3g.

the cake had been excited by Mr. Wheler ; but they had no regular revolutions
at all, though several very manifest motions were made with the hand, to try if
a projectile motion might by that means be given to the pendulous body. Mr.
Wheler had tried the same thing with his servant ; from whence it is reasonable
to conclude, that it is necessary, that the same person who excited the cake,
should likewise hold the thread ; as if there were some analogy between the
effluvia excited by the clapping of the hand on the cake, and the effluvia which
may be communicated along from the hand which holds the thread to the piece
of cork at the end of it. And this seems to be the reason of what the late Mr.
Grey said, viz. That there was something in the human hand essential to
the experiment, which he had not yet found in any other supporter of the
thread.

Some Remarks on the Electrical Circular Experiment* of the late Stephen
Gray, F.R.S. By Granvile Wheler, Esq. N° 453, p. 118.

Some uncommon circumstances led Mr. W. to make Mr. Gray's circular
experiment in the following manner. While he excited a cake of rosin and
bees-wax, 10 inches diameter, by clapping with his hand, he let the ivory ball
remain in a basin of water ; then shaking off the drops, placed it in the cen-
tre, and with his right hand held a fine thread, about 8 or Q inches long, having
one end rolled up into a little ball, and the other, for about an inch, reduced
to its greatest fineness, to only one fibre, himself and hand being supported on
the back of a chair. The success was, he had a great many revolutions, to the
number of 50, from west to east ; but at first not so regular as towards the
last, at first describing only about 1 -third part of the circumference at a
time, and after standing still a little, describing another third part. He might
probably have had a great many more revolutions, but being tired, he was
forced to rest himself, which he did for 10 minutes, then took up the thread
again. The thread stood repelled at some distance, without making any revo-
lutions, and at last only made half a one the contrary way to what it did be-
fore; but on wetting it, by drawing it 2 or 3 times over the surface of the
water, it made again 20 more revolutions from west to east, only at a smaller
distance from the ball, for the water must make it heavier, but full as regular
as before, and rather quicker. The virtue of the cake must now have lasted
about 3 quarters of an hour. After resting about 6 minutes, he tried again
with the string fresh wetted, the ball and cake continuing as before; and had,
to his great surprise, 100 revolutions in the space of about 12 minutes, the

* See Philos. Trans. N" 441, 444, of the Revolutions of pendulous bodies by electricity. — Orig.



VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 317

revolutions being still quicker, and more regular, and nearer the ball ; and at
the 6th revolution of this last hundred, the thread was attracted to the surface
of the ball, and, being wet, did not disengage itself, till pulled away ; yet
after this, it described the remaining 9«1 revolutions of the hundred, and seemed
inclined to describe a great many more, but that he was forced to rest his arm
again, which he did for about 8 minutes, then tried again, the thread being
fresh wetted, and had 70 revolutions at nearly the same distance from the ball
in less than 9 minutes, all very regular, and without any attraction of the
thread to the ball. He rested again 16 minutes, wet the thread again, and
held it as usual; it was repelled at about -^ inch distance from the ball, but
seemed to have no tendency to a circular motion ; yet after continuing stationary
about a minute, he perceived a motion about its axis, about which it took
several turns; but still had little or no progressive motion, till about a minute
longer, when it began to move forward, and continued doing so from west to
east, for about 33 revolutions, very regular, but slower than in the last two
cases, the string having been held about 10 minutes, and the revolutions per-
formed in about 7 or 8 of them. In each of these last 3 times, it whs rather
longer before the progressive motion began than usual; and in all the trials
of this experiment, he frequently perceived a motion about the axis, which was
generally from west to east, though now and then the contrary way. The
virtue of the cake n)ust now have lasted near 2 hours ; about 3 quarters of an
hour after, he tried again, and had 60 revolutions from west to east, in about
10 minutes, the distance from the ball being still less than before, hardly -j- of
an inch, scarcely any revolution about the axis appeared, and at the beginning
the thread was twice attracted to the ball. About an hour and a half after,
the virtue of the ball was not quite gone, the wet thread being repelled, and
making 3 or 4 revolutions from west to east, as well as moving a little about
its axis the same way. But as it was reasonable to suppose the ball itself in
the centre of the cake was now dry, with a feather dipped in water he wetted
its surface ; yet found no increase of virtue, rather a diminution of it, the
pendulous body seeming scarcely at all repelled; but it is to be observed, that
the ball, as it was wetting, twice tumbled over, and rolled on the surface
of the cake; by which means the virtue of the cake might be much di-
minished.

It is not improper too to take notice here, that during the revolutions of the
wet string, he frequently observed a kind of oscillatory motion, as if there was
an alternate intention and remission of the repulsive force. As also that he
often took notice of little plucks, and convulsive motions, in the pendu-
lous body, and sometimes thought he has felt something like it in his



318 PHILOSOPHICAL TRANSACTIONS. [aNNO 1739.

arm that held it, though at no other time has he ever been sensible of any
such thing.

He several times after repeated this experiment with the thread and ball both
wet, and found it succeed much better than when they were both dry ; and
once he had 220 revolutions before he rested his arm. He tried too with the
ball dry, and the string only made wet ; but the virtue did not continue so
long, as when both were wet.

He now flattered himself with hopes of success, if the thread was suspended
from an undoubted fixed point, which therefore he proceeded again to try with
the greatest care and caution, but in vain; the revolutions were uncertain.

This ditFerence naturally led him to reflect on the cause of it. The tremor
of the hand would not account for it ; for this being both ways backward as
well as forward, must as often hinder as promote a continual motion one way:
and though in two opposite parts of a circle, the motion is really in contrary
directions, and therefore the contrary impulses of a tremor may promote a re-
volution applied at opposite places of the orbit ; yet as these tremors are irre-
gular, and succeed much quicker than the revolutions are performed, they seem
insufficient to account for the motions of the pendulous body, performed with
any degree of regularity.

A stream of air in the room might impel along the tangent the pendulous
body, kept at a distance from the ball by its repulsive force ; and then gravity,
taking place, might with the first motion compound a curve: but still the re-
sistance of the air would soon destroy the original impulse, could a few revo-
lutions be performed; and besides, one revolution could not be performed,
because the same stream of air that began the motion, must be contrary to it
in its return.

A finger held on the right hand near the pendulous body, when suspended
from a fixed point, will make it revolve from west to east; but then it must
be applied and removed alternately : the repulsive force therefore which the arm
may acquire, by being held in the sphere of the effluvia, is insufficient ; for,
as it is in one place, it must impel only one way, and constantly the same way;
and therefore, like a stream of air in the room, though it might create the
beginning, it must binder the completion of a revolution.

Sometimes he doubted, whether the pulse of the arm might not be assisting
in giving a projectile motion. When one leg is laid over the knee of the
other, a motion and heaving of the leg that lies over, answering to every stroke
of the pulse, is very apparent at a distance : the arm therefore in some posi-
tions, in which its great artery meets with a proportionable pressure or resist-
ance, may have a constant motion, though less perceivable.



VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. SIQ

What seemed the most probable sohition, was this : when the arm is ex-
tended, the posture being uneasy, there must be a re-action of the muscles, or
a continual pulling of the arm towards the body. When therefore the right
arm is made use of, the pulling will be from right to left; and consequently
the motion produced in the body held by it in the same direction, or from west
to east. When the left arm is made use of, the re-action of the muscles will
be from left to right, and therefore the motion of the pendulous body from
east to west. And, agreeably to this, he has observed, when he used his left
hand, all other circumstances continuing the same, the motion of the pendu-
lous body was from left to right, or from east to west, contrary to what was
observed when held by the right hand. Yet still neither of these solutions
would account for the variety of odd particulars he has met with under various
circumstances.

He proceeded therefore to try with rests for his arm of different heights,
having an arm of wood, about 2 feet long, fixed to a rest for his telescopes,
which could be raised to any height wanted ; and then the experiment succeeds
only well, when the rest was lower than the electric area, and the arm was sup-
ported on its elbow, which was the posture constantly made use of, when
rested on a chair, the chair being lower than the electric area, that it might
less affect the effluvia, as was then thought.

He began now to think, whether it was not possible, that an inclination to
a motion one way in the person that holds the body, might not have such an
influence on the arm, and consequently the string and pendulous body, as to
determine them the same way by some pressure or bias put upon it, though
no motion sensible, even to himself, was produced in the hand. If so, he
might, by a contrary inclination, produce a motion the contrary way. Having
therefore a fine day, and the circular cake being well excited, he tried if he



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 37 of 85)