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nothing philosophical or real in them. I have been happy thus
far in meeting with the most honourable and candid though most
sanguine persons, and I believe the mental check which I propose
will be available in the hands of all who desire truly to investigate
the philosophy of the subject, and, being con tent to resign expec-
tation, wish only to be led by the facts and the truth of nature.
As I am unable, even at present, to answer all the letters that
come to me regarding this matter, perhaps you will allow me
to prevent any increase by saying that my apparatus may be seen
at the shop of the philosophical instrument maker Newman,
122 Regent-street. Permit me to say, before concluding, that
I have been greatly startled by the revelation which this purely
physical subject has made of the condition of the public mind.
No doubt there are many persons who have formed a right
judgment or used a cautious reserve, foi I know several such,



1853.] Experimental Investigation of Table-Moving. 385

and public communications have shown it to be so ; but their
number is almost as nothing to the great body who have believed
and borne testimony, as I think, in the cause of error. I do
not here refer to the distinction of those who agree with me
and those who differ. By the great body, I mean such as reject
all consideration of the equality of cause and effect, who refer
the results to electricity and magnetism, yet know nothing of
the laws of these forces, or to attraction, yet show no phe-
nomena of pure attractive power, or to the rotation of the earth,
as if the earth revolved round the leg of a table, or to some
unrecognized physical force, without inquiring whether the
known forces are not sufficient, or who even refer them to
diabolical or supernatural agency, rather than suspend their
judgment, or acknowledge to themselves that they are not
learned enough in these matters to decide on the nature of the
action. I think the system of education that could leave the
mental condition of the public body in the state in which this
subject has found it, must have been greatly deficient in some
very important principle.

I am, Sir, your very obedient Servant,
Royal Institution, June 28, 1853. M. FARADAY.



Experimental Investigation of Table- Moving*.
THE object which I had in view in this inquiry was not to
satisfy myself, for my conclusion had been formed already on
the evidence of those who had turned tables ; but that I
might be enabled to give a strong opinion, founded on facts,
to the many who applied to me for it. Yet the proof which I
sought for, and the method followed in the inquiry, were
precisely of the same nature as those which I should adopt in
any other physical investigation. The parties with whom I
have worked were very honourable, very clear in their inten-
tions, successful table-movers, very desirous of succeeding in
establishing the existence of a peculiar power, thoroughly
candid, and very effectual. It is with me a clear point that the
table moves when the parties, though they strongly wish it, do
not intend, and do not believe that they move it by ordinary
mechanical power. They say, the table draws their hands ;
* Athemeum, July 2, 1853.



386 Experimental Investigation of Table- Moving. [1853.

that it moves first, and they have to follow it, that sometimes
it even moves from under their hands. With some the table
will move to the right or left according as they wish or will it,
with others the direction of the first motion is uncertain :
but all agree that the table moves the hands and not the hands
the table. Though I believe the parties do not intend to move
the table, but obtain the result by a quasi involuntary action,
still I had no doubt of the influence of expectation upon their
minds, and through that upon the success or failure of their
efforts. The first point, therefore, was to remove all objections
due to expectation, having relation to the substances which I
might desire to use : so, plates of the most different bodies,
electrically speaking, namely, sand-paper, millboard, glue,
glass, moist clay, tinfoil, cardboard, gutta percha, vulcanized
rubber, wood, &c., were made into a bundle and placed on a
table under the hands of a turner. The table turned. Other
bundles of other yjlates were submitted to different persons at
other times, and the tables turned. Henceforth, therefore,
these substances maybe used in the construction of apparatus.
Neither during their use nor at other times could the slightest
trace of electrical or magnetic effects be obtained. At the
same trials it was readily ascertained that one person could
produce the effect ; and that the motion was not necessarily
circular, but might be in a straight line. No form of experi-
ment or mode of observation that I could devise gave me the
slightest indication of any peculiar natural force. No attrac-
tions, or repulsions, or signs of tangential power, appeared,
nor anything which could be referred to other than the mere
mechanical pressure exerted inadvertently by the turner. I
therefore proceeded to analyse this pressure, or that part of it
exerted in a horizontal direction: doing so, in the first instance,
unawares to the party. A soft cement, consisting of wax and
turpentine, or wax and pomatum, was prepared. Four or five
pieces of smooth slippery cardboard were attached one over
the other by little pellets of the cement, and the lower of these
to a piece of sand-paper resting on the table ; the edges of
these sheets overlapped slightly, and on the under surface a
pencil line was drawn over the laps so as to indicate position.
The upper cardboard was larger than the rest, so as to cover
the whole from sight. Then the table-turner placed the hands



1853.] Experimental Investigation of Table-Moving. 387

upon the upper card, and we waited for the result. Now, the
cement was strong enough to offer considerable resistance to
mechanical motion, and also to retain the cards in any new
position which they might acquire, and yet weak enough to
give way slowly to a continued force. When at last the tables,
cards, and hands all moved to the left together, and so a true
result was obtained, I took up the pack. On examination it
was easy to see by the displacement of the parts of the line,
that the hand had moved further than the table, and that the
latter had lagged behind ; that the hand, in fact, had pushed
the upper card to the left, and that the under cards and the
table had followed and been dragged by it. In other similar
cases when the table had not moved, still the upper card was
found to have moved, showing that the hand had carried it in
the expected direction. It was evident, therefore, that the
table had not drawn the hand and person round, nor had it
moved simultaneously with the hand. The hand had left all
things under it behind, and the table evidently tended con-
tinually to keep the hand back.

The next step was to arrange an index which should show
whether the table moved first, or the hand moved before the
table, or both moved or remained at rest together. At first
this was done by placing an upright pin fixed on a leaden foot
upon the table, and using that as the fulcrum of a light lever*
The latter was made of a slip of foolscap paper, and the short
arm, about ^ of an inch in length, was attached to a pin
proceeding from the edge of a slipping card placed on the
table, and prepared to receive the hands of the table-turner.
The other arm, of ll| inches long, served for the index of
motion. A coin laid on the table marked the normal position
of the card and index. At first the slipping card was attached
to the table by the soft cement, and the index was either
screened from the turner, or the latter looked away : then,
before the table moved, the index showed that the hand was
giving a resultant pressure in the expected direction. The
effect was never carried far enough to move the table, for the
motion of the index corrected the judgment of the experi-
menter, who became aware that, inadvertently, a side force
had been exerted. The card was now set free from the table,
i. e. the cement was removed. This, of course, could not



888 Experimental Investigation of Talle- Moving. [1853.

interfere with any of the results expected by the table-turner,
for both the bundle of plates spoken of and single cards
had been freely moved on the tables before ; but now that
the index was there, witnessing to the eye, and through it
to the mind, of the table-turner, not the slightest tendency to
motion either of the card or of the table occurred. Indeed,
whether the card was left free or was attached to the table, all
motion or tendency to motion was gone. In one particular
case there was relative motion between the table and the
hands : I believe that the hands moved in one direction ; the
table-turner was persuaded that the table moved from under
the hand in the other direction : a gauge, standing upon the
floor, and pointing to the table, was therefore set up on that
and some future occasions, and then, neither motion of the
hand nor of the table occurred.

A more perfect lever apparatus was then constructed in the
following manner : Two thin boards, 9^ inches by 7 inches,
were provided ; a board, 9 inches by 5 inches, was glued to the
middle of the underside of one of these (to be called the table-
board), so as to raise the edges free from the table ; being placed
on the table, near and parallel to its side, an upright pin was
fixed close to the further edge of the board, at the middle, to
serve as the fulcrum for the indicating lever. Then four glass
rods, 7 inches long and in diameter, were placed as rollers on
different parts of this table-board, and the upper board placed
on them ; the rods permitted any required amount of pressure
on the boards, with a free motion of the upper on the lower to
the right and left. At the part corresponding to the pin in
the lower board, a piece was cut out of the upper board, and
a pin attached there, which, being bent downwards, entered
the hole in the end of the short arm of the index lever : this
part of the lever was of cardboard ; the indicating prolongation
was a straight hay-stalk 15 inches long. In order to restrain
the motion of the upper board on the lower, two vulcanized
rubber rings were passed round both, at the parts not resting
on the table : these, whilst they tied the boards together,
acted also as springs, and whilst they allowed the first feeblest
tendency to motion to be seen by the index, exerted, before the
upper board had moved a quarter of an inch, sufficient power
in pulling the upper board back from either side, to resist a



1853.] Experimented Investigation of Table-Moving. 389

strong lateral action of the hand. All being thus arranged,
except that the lever was away, the two boards were tied
together with string, running parallel to the vulcanized rubber
springs, so as to be immoveable in relation to each other. They
were then placed on the table, and a table-turner sat down to
them : the table very shortly moved in due order, showing
that the apparatus offered no impediment to the action. A
like apparatus, with metal rollers, produced the same result
under the hands of another person. The index was now put
into its place and the string loosened, so that the springs should
come into play. It was soon seen, with the party that could
will the motion in either direction (from whom the index was
purposely hidden), that the hands were gradually creeping up
in the direction before agreed upon, though the party certainly
thought they were pressing downwards only. When shown that
it was so, they were truly surprised ; but when they lifted up
their hands and immediately saw the index return to its normal
position, they were convinced. When they looked at the
index and could see for themselves whether they were pressing
truly downwards, or obliquely so as to produce a resultant in
the right- or left-handed direction, then such an effect never
took place. Several tried, for a long while together, and with
the best will in the world ; but no motion, right or left, of
the table, or hand, or anything else occurred. [Then occurs a
passage from the ' Times,' already printed at pp. 383, 384-.]

Another form of index was applied thus : a circular hole
was cut in the middle of the upper board, and a piece of
cartridge paper pasted under it on the lower surface of the
board ; a thin slice of cork was fixed on the upper surface of
the lower board corresponding to the cartridge paper; the
interval between them might be a quarter of an inch or less.
A needle was fixed into the end of one of the index hay-stalks,
and when all was in place the needle point was passed through
the cartridge paper and pressed slightly into the cork beneath,
so as to stand upright : then any motion of the hand, or hand-
board, was instantly rendered evident by the deflection of the
perpendicular hay-stalk to the right or left.

I think the apparatus I have described may be useful to
many who really wish to know the truth of nature, and would
prefer that truth to a mistaken conclusion ; desired, perhaps



390 Experimental Investigation of Table-Moving. [1853.

only because it seems to be new or strange. Persons do not know
how difficult it is to press directly downward, or in any given
direction against a fixed obstacle, or even to know only whether
they are doing so or not; unless they have some indicator,
which, by visible motion or otherwise, shall instruct them:
and this is more especially the case when the muscles of the
fingers and hand have been cramped and rendered either
tingling, or insensible, or cold by long-continued pressure.
If a finger be pressed constantly into the corner of a window-
frame for ten minutes or more, and then, continuing the
pressure, the mind be directed to judge whether the force at
a given moment is all horizontal, or all downward, or how
much is in one direction and how much in the other, it will
find great difficulty in deciding ; and will at last become
altogether uncertain : at least such is my case. I know that a
similar result occurs with others ; for I have had two boards
arranged, separated, not by rollers, but by plugs of vulcanized
rubber, and with the vertical index : when a person with
his hands on the upper board is requested to press only
downwards, and the index is hidden from his sight, it
moves to the right, to the left, to him and from him, and in
all horizontal directions ; so utterly unable is he strictly to
fulfil his intention without a visible and correcting indicator.
Now, such is the use of the instrument with the horizontal
index and rollers : the mind is instructed, and the involuntary
or quasi involuntary motion is checked in the commencement,
and therefore never rises up to the degree needful to move
the table, or even permanently the index itself. No one can
suppose that looking at the index can in any way interfere
with the transfer of electricity or any other power from the
hand to the board under it or to the table. If the board tends
to move, it may do so, the index does not confine it; and if
the table tends to move, there is no reason why it should not.
If both were influenced by any power to move together, they
may do so, as they did indeed when the apparatus was tied,
and the mind and muscles left unwatched and unchecked.

I must bring this long description to a close. I am a little
ashamed of it, for I think, in the present age, and in this part of
the world, it ought not to have been required. Nevertheless
I hope it may be useful. There are many whom I do not



^857.] Experimental Relations of Gold to Light 391

expect to convince ; but I may be allowed to say that I cannot
undertake to answer such objections as may be made. I state
my own convictions as an experimental philosopher, and find
it no more necessary to enter into controversy on this point
than on any other in science, as the nature of matter, or
inertia, or the magnetization of light, on which I may differ
from others. The world will decide sooner or later in all such
cases, and I have no doubt very soon and correctly in the
present instance. Those who may wish to see the particular
construction of the test apparatus which I have employed, may
have the opportunity at Mr. Newman's, 122 Regent Street.
Further, I may say, I have sought earnestly for cases of lifting
by attraction, and indications of attraction in any form, but
have gained no traces of such effects. Finally, I beg to direct
attention to the discourse delivered by Dr. Carpenter at
the Royal Institution on the 12th of March, 1S52, entitled,
" On the Influence of Suggestion in modifying and directing
Muscular Movement, independently of Volition;" which,
especially in the latter part, should be considered in reference
to table-moving by all who are interested in the subject.
Royal Institution, June 27. M. FARADAY.



THE BAKERIAN LECTURE. Experimental Relations of Gold

(and other Metals] to LigJit*.
[Received November 15, 1856, Read February 5, 1857.]
THAT wonderful production of the human rnind, the undulatory
theory of light, with the phenomena for which it strives to
account, seems to me, who am only an experimentalist, to stand
midway between what we may conceive to be the coarser mecha-
nical actions of matter, with their explanatory philosophy, and
that other branch, which includes, or should include, the phy-
sical idea of forces acting at a distance ; and admitting for the
time the existence of the ether, I have often struggled to perceive
how far that medium might account for or mingle in with such
actions generally ; arid to what extent experimental trials might
be devised, which, with their results and consequences, might
contradict, confirm, enlarge, or modify the idea we form of it,
always with the hope that the corrected or instructed idea would

* Philosophical Transactions, 1857, p. 145.



392 On the Experimental Relations [1857.

approach more and more to the truth of nature, and in the
fulness of time coincide with it.

The phenomena of light itself are, however, the best and
closest tests at present of the undulatory theory ; and if that
theory is hereafter to extend to and include other actions, the
most effectual means of enabling it to do so will be to render
its application to its own special phenomena clear and sufficient.
At present the most instructed persons are, I suppose, very far
from perceiving the full and close coincidence between all the
facts of light and the physical account of them which the theory
supplies. If perfect, the theory would be able to give a reason
for every physical affection of light ; whilst it does not do so,
the affections are in turn fitted to develope the theory, to extend
and enlarge it if true, or if in error to correct it or replace it by
a better. Hence my plea for the possible utility of experiments
and considerations such as those I am about to advance.

Light has a relation to the matter which it meets with in its
course, and is affected by it, being reflected, deflected, trans-
mitted, refracted, absorbed, &c. by particles very minute in
their dimensions. The theory supposes the light to consist of
undulations, which, though they are in one sense continually
progressive, are at the same time, as regards the particles of
the ether, to and fro transversely. The number of progressive
alternations or waves in an inch is considered as known, being
from 37,600 to 59,880, and the number which passes to the eye
in a second of time is known also, being from 458 to 727 billions ;
but the extent of the lateral excursion of the particles of the
ether, either separately or conjointly, is not known, though both
it and the velocity are probably very small compared to the
extent of the wave and the velocity of its propagation. Colour
is identified with the number of waves. Whether reflexion,
refraction, &c., have any relation to the extent of the lateral
vibration, or whether they are dependent in part upon some
physical action of the medium unknown to and unsuspected by
us, are points which I understand to be as yet undetermined.

Conceiving it very possible that some experimental evidence
of value might result from the introduction into a ray of separate
particles having great power of action on light, the particles
being at the same time very small as compared to the wave-
lengths, I sought amongst the metals for such. Gold seemed



1857.] of Gold (and other Metals) to Light. 393

especially fitted for experiments of this nature, because of its
comparative opacity amongst bodies, and yet possession of a
real transparency ; because of its development of colour both
in the reflected and transmitted ray; because of the state of
tenuity and division which it permitted with the preservation
of its integrity as a metallic body ; because of its supposed
simplicity of character ; and becauseknown phenomena appeared
to indicate that a mere variation in the size of its particles gave
rise to a variety of resultant colours. Besides, the waves of
light are so large compared to the dimensions of the particles
of gold which in various conditions can be subjected to a ray,
that it seemed probable the particles might come into effective
relations to the much smaller vibrations of the ether particles ;
in which case, if reflexion, refraction, absorption, &c., depended
upon such relations, there was reason to expect that these
functions would change sensibly by the substitution of different
sized particles of this metal for each other. At one time I hoped
that I had altered one coloured ray into another by means of
gold, which would have been equivalent to a change in the num-
ber of undulations ; and though I have not confirmed that result
as yet, still those I have obtained seem to me to present a useful
experimental entrance into certain physical investigations re-
specting the nature and action of a ray of light. I do not pretend
that they are of great value in their present state, but they are
very suggestive, and they may save much trouble to any experi-
mentalist inclined to pursue and extend this line of investigation.

Gold-leaf effect of heat, pressure, $c.

Beaten gold-leaf is known in films estimated at the 28 / uo0 th
of an inch in thickness ; they are translucent, transmitting green
light, reflecting yellow, and absorbing a portion. These leaves
consist of an alloy in the proportions of 12 silver and 6 copper
to 462 of pure gold. 2000 leaves 3ths of an inch square are
estimated to weigh 384 grains. Such gold-leaf is no doubt full
of holes, but having, in conjunction with Mr. W. De la Rue,
examined it in the microscope with very high powers (up to
700 linear), we are satisfied that it is truly transparent where
the gold is continuous, and that the light transmitted is green.
By the use of the balance Mr. De la Rue found that the leaf
employed was on the average irwDirth of an inch thick.



394 On the Experimental Relations [1857.

Employing polarized light and an arrangement of sulphate of
lime plates, it was found that other rays than the green could
be transmitted by the gold-leaf. The yellow rays appeared to
be those which were first stopped o.i thrown back. Latterly I
have obtained some pure gold-leaf beaten by Marshall, of which
5000 leaves weighed 408 grains, or 0*2 of a grain per leaf: its
reflected colour is orange-yellow, and its transmitted colour a
warm green. Gold alloy containing 5 per cent, of silver pro-
duces pale gold-leaf, which transmits a blue purple light, and
extinguishes much more than the ordinary gold-leaf.

So a leaf of beaten gold occupies in average thickness no
more than from jth to ^th part of a single wave of light. By
chemical means, the film may be attenuated to such a degree as
to transmit a ray so luminous as to approach to white, and that
in parts which have every appearance of being continuous in
the microscope, when viewed with a power of 700. For this
purpose it may be laid upon a solution of chlorine, or, better
still, of the cyanide of potassium*. If a clean plate of glass be
breathed upon and then brought carefully upon a leaf of gold,
the latter will adhere to it; if distilled water be immediately
applied at the edge of the leaf, it will pass between the glass
and gold, and the latter will be perfectly stretched ; if the water
be then drained out, the gold-leaf will be left well extended,
smooth, and adhering to the glass. If, after the water is poured
off, a weak solution of cyanide be introduced beneath the gold,



Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 38 of 49)