_The Thaumatrope.--A great improvement effected in its
construction.--Another toy upon the same optical principle._
Tom’s holidays were now drawing to a close, and the children were
summoned into the library to receive their last lesson in philosophy.
“You have lately witnessed an experiment,” said Mr. Seymour, “which
must have convinced you how liable the ear is to be deluded with
respect to the nature and direction of sound; I shall now show you that
the eye has also its sources of fallacy.”
“If you proceed in this manner, you will make us all Cartesians,”[63]
exclaimed the vicar.
“I shall illustrate my subject by means of a new toy which I have
lately invented,” said Mr. Seymour, “and unless I am much mistaken, it
will afford as much amusement to the elder as to the younger members of
our party, although the vicar may perhaps regard it as a more hostile
instrument than even that of the wooden horse which filled unhappy Troy
with an armed enemy. It is a small machine,” continued Mr. Seymour,
“which is well calculated to furnish us with some capital puns.”
“With puns!” exclaimed the horrified vicar, who no sooner heard this
appalling declaration, than like another Laocoon, he deprecated the
introduction of the “_donum exitiale_” within the walls of Overton
Lodge. But his hostility was soon disarmed, not by the circumvolutions
of a snake around the body of the enraged orator, but by the embraces
of little Rosa, who threw her arms around the neck of the vicar, with
such supplicating grace, that at length he exclaimed, “Well, well; if
it be the decree of the Fates, I must submit.”
During this altercation, Mr. Seymour had procured the “wooden engine”
from his study.
“I will first,” said he, “exhibit the toy in its original state, and
then show you the improvements which have been effected in it.”
“Let us hear the account of its operation,” said the major, “which I
perceive is enclosed within the box.”
“True,” replied Mr. Seymour; “and I think you will agree that I have
given a very plausible explanation of its effects.”
“Plausible,” muttered the vicar, “plausible enough, no doubt; oh the
Sinon!”
Mr. Seymour then proceeded. “This toy is termed the THAUMATROPE.”
“Of Grecian origin!” observed the vicar. “‘_Timeo Danaos et dona
ferentes_,’ as Virgil has it.”
“What is the meaning of the term?” asked Louisa. The vicar explained to
her that it was compounded of the Greek words, θαυηα, and τρεπω; the
former of which signified _wonder_, the latter _to turn_.
“Exactly,” replied Mr. Seymour. “‘_A Wonder-turner_,’ or a toy which
performs wonders by turning round: but let me proceed in the
explanation.” He then continued to read as follows: “This philosophical
toy is founded upon the well-known optical principle, that an
impression made on the retina of the eye lasts for a short interval
after the object which produced it has been withdrawn. During the rapid
whirling of the card, the figures on each of its sides are presented
with such quick transition, that they both appear at the same instant,
and thus occasion a very striking and magical effect. On each of these
cards a device is introduced, with an appropriate motto, or epigram;
the point of which is answered, or explained, by the change which the
figure assumes during the rapid whirling of the card.”
“It may be very clever,” said the vicar, “but I do not understand it.”
“But you shortly will; look at one of the cards.”
Mr. Seymour then displayed a pasteboard circle, on the one side of
which was figured a rat, and on the other, a cage; two strings were
fastened in its axis, by which the card could easily be made to
revolve, by means of the thumb and finger. Fearing that some of our
readers may be as dull of comprehension as the vicar, we have
introduced a sketch of the apparatus, in which both sides of the card
are exhibited, with the strings by which it is whirled round.
[Illustration: Two circular cards with strings attached, one with an
empty cage and one with a rat.]
No sooner had Mr. Seymour put the card in motion, than the vicar, in a
tone of the greatest surprise, exclaimed, “Magic! magic! I declare the
rat is in the cage!!”
“And what is the motto?” asked Louisa.
“Why is this rat like an opposition member in the House of Commons, who
joins the ministry?” replied Mr. Seymour.
“Ha, ha, ha!--excellent!” cried the major, as he read the following
answer: “because by _turning round_ he gains a snug berth, but ceases
to be free.”
“The very reverse to what occurred in ancient Rome, where the slave
became free by turning round,” observed the vicar.
The vicar, no doubt, alluded to the custom of making a freeman, as
described by Persius; from which it appears, that the clapping a cap on
the head, and giving him a turn on the heel, were necessary
circumstances. A slave thus qualified became a citizen of Rome, and was
honoured with a name more than belonged to any of his forefathers,
which Persius has repeated with a great deal of humour in his 5th
satire:--
“----Heu steriles veri, quibus una Quiritem
Vertigo facit!”
“That false enfranchisement with ease is found;
Slaves are made citizens by turning round.”
DRYDEN.
“Show us another card,” said Tom, eagerly.
“Here then is a watch-box; when I turn it round, you will see the
watchman comfortably sleeping at his post.”
“Very good! It is very surprising,” said the vicar.
“Yes,” observed the major; “and to carry on your political joke, it may
be said that, like most worthies who gain a post, by _turning round_,
he sleeps over his duty.”
“The epigram which accompanies it is not deficient in point,” said Mr.
Seymour.
“The caprice of this watchman surpasses all bound
He ne’er sits in his box, but when going his _round_
While he no sooner rests, ’tis a strange paradox!
Than he flies from his post, and _turns_ out of his box.”
“What have you there?” exclaimed the vicar; “arms and legs, without a
body?”
“Yes,” replied Mr. Seymour; “and which, on turning round, will present
the figure of a king, invested with all the insignia of royalty.”
“It is indeed a king. Look at his crown and sceptre!” cried Louisa.
“Now for the epigram,” said the major, who then read the following
lines:--
“Head, legs, and arms, alone appear;
Observe that _nobody_ is here;
Napoleon-like I undertake
Of nobody a king to make.”
The next card presented a laughing face, which on being turned round,
was instantly changed into a weeping one. The motto--_The sweetest
things turn sour_.
“The device is capital!” exclaimed the vicar, “I question whether Peter
of Cortona ever produced a more striking metamorphosis.”[64]
The other cards were now exhibited in succession, of which the box
contained eighteen, and the whole party, not even excepting the vicar,
were highly gratified with the amusement.
“But I have not yet read to you the author’s address to the public; and
which, I must say, contains a succession of very happy puns.”
“Spare me! spare me!” cried the vicar: “I like your toy, but cannot
discover the advantage of alloying amusement with such spurious wit,
and of associating science with buffoonery.”
Mr. Seymour, however, was relentless, and thus proceeded: “It is well
known that the Laputan philosopher invented a piece of machinery, by
which works could be composed by a mechanical operation; and the
Quarterly Review has asserted, that a certain English poem was
fabricated in Paris, by the powers of a steam-engine; but the author of
the present invention claims for himself the exclusive merit of having
first constructed a hand-mill, by which puns and epigrams may be
_turned_ with as much ease as tunes are played on the hand-organ, and
old jokes so _rounded_ and changed, as to assume all the airs of
originality. The inventor confidently anticipates the favour and
patronage of an enlightened and liberal public, on the well-grounded
assurance, that ‘_one good turn_ deserves another;’ and he trusts that
his discovery may afford the happy means of giving activity to wit that
has been long _stationary_; of _revolutionising_ the present system of
_standing_ jokes, and of putting into _rapid circulation_ the most
approved bon-mots.”
“Why, vicar, what ails thee?” exclaimed the major.
“Our subject has given him a _turn_; let him alone, and he will soon
_come round_,” observed Mr. Seymour.
The whole party, with the exception of Mr. Twaddleton, laughed
heartily; the vicar, however, did not relax a feature of his
countenance.
As soon as this ebullition had subsided, the major enquired of Mr.
Seymour, what was the nature of the improvement to which he had alluded.
“My proposed improvements refer both to the subjects exhibited on the
cards, and to the mechanism by which their changes are effected,”
replied Mr. Seymour.
“In the first place, it has occurred to me that this amusing toy might
be made instrumental in impressing classical subjects upon the memory
of young persons.”
This observation delighted the vicar, who said that he would patronise
such an attempt with all his heart.
“Why can we not,” continued he, “thus represent the Metamorphoses of
Ovid; or what say you, vicar, to converting the fleet of Æneas into
sea-nymphs, as Virgil has it?”
“An elegant thought! upon my word; a most elegant conception!”
exclaimed Mr. Twaddleton.
“What have we here?” interrupted the major, who had, for the first
time, noticed the superscription on the cover of the box: “had I seen
this before, I should have augured favourably of the toy: it is like
the sign of an inn, which is held out to announce good entertainment
within.” He then read the following:--
The Thaumatrope;
being
_Rounds_ of Amusement,
or
How to please and surprise
By _Turns_.
Mr. Seymour now proceeded to explain more fully the optical theory of
the instrument, which neither Louisa nor Tom could, as yet, thoroughly
understand.
He told them that an object was seen by the eye, in consequence of its
image being delineated on the retina, or optic nerve, which is situated
on the back part of the eye; and that it had been ascertained, by
experiment, that the impression which the mind thus receives, lasts for
about the eighth part of a second after the image is removed. “It is,
therefore, sufficiently evident,” said Mr. Seymour, “that if any point,
as a lighted stick, be made to revolve, so as to complete the circle in
that period, we shall not see a fiery point, but a fiery circle;
because the impression made by it in every point of its circuit will
remain until it comes round again to the spot from which it set
out;--but we will, at once, exemplify this fact by an experiment.”
Tom was accordingly directed to procure a piece of stick and a candle;
and as soon as they were brought into the room, Mr. Seymour ignited the
end of the stick and whirled it round, when a bright circle, without
any intervals of darkness, was seen by the whole party.
“Never until this instant,” exclaimed the vicar, with an expression of
high satisfaction, “did I fully appreciate the beauty of that passage
in Milton, wherein the poet evidently describes the rapidity of Satan’s
flight, as well as the refulgence of his appearance--
“‘Sprung upward like a pyramid of fire.’
“Now to take in the full meaning of this figure,” continued Mr.
Twaddleton, “we must imagine ourselves in chaos, and that a vast
luminous body is rising near the spot where we may be supposed to be
standing, so swiftly as to appear a continued track of light, and
lessening to the view, according to the increase of distance, until it
ends in a point, and then disappears; and all this must be supposed to
strike our eye at one instant.”
“It is very probable,” said Mr. Seymour, “that the poet had such an
idea in view, and that he intended by it to convey the immense rapidity
of Satan’s flight. Homer makes use of the same figure to express the
velocity of the javelin, δολιχοσκιον εγχος, the ‘_long shadowed_’
javelin. We shall have ample proof of the effect of this power in the
eye of retaining impressions, and of thus converting points into lines
and circles, during the exhibition of your fire-works; and which, in
fact, derive the greater part of their magical effect from it.”
“The pin wheel is certainly nothing more than a fiery circle produced
by the rapid revolution of a jet of flame,” said the vicar.
“And the rocket,” added Mr. Seymour, “is a column of light occasioned
by the same rapid movement of a burning body in a rectilinear or curved
direction.”
“I perfectly understand all that you have said,” observed Tom.
“Then you will not have any difficulty in explaining the action of the
Thaumatrope, for it depends upon the same optical principle; the
impression made on the retina by the image, which is delineated on one
side of the card, is not erased before that which is painted on the
opposite side is presented to the eye; and the consequence is, that you
see both sides at once.”
“Or, you might put it in this way,” said the major: “that as the image
remains the eighth of a second on the retina, after it has been
withdrawn from the eye, a revolution of eight times in a second will
secure its uninterrupted continuance.”
“On turning round the card,” observed Louisa, “I perceive that every
part of the figure is not equally distinct.”
“Because every part of the card does not revolve with the same
velocity,” said her father; “and this fact offers a good illustration
of what I formerly stated,[65] that in circular motion, the parts more
remote from the axis of rotation are those which move with the greater
velocity. This toy will also be found capable of exemplifying another
truth to which I have before alluded, that ‘the axis of motion remains
at rest while all the parts revolve round it.’”[66]
“I remember that very well,” exclaimed Tom.
“Then take the card, and spin it between yourself and the window, and
tell me what you observe,” said his father.
“I see a dark line across the window; and what is very strange, the
other parts of the card appear transparent; for they do not obstruct
the view of the window, as they would if the card were at rest.”
“The dark line you see is the axis of rotation, which being stationary,
necessarily excludes the light; the other parts being in motion do not
remain a sufficient time to obliterate the image made on the eye by the
window. It is true that the card disc passes between your eye and the
light, but as it does not continue at any one point for more than the
eighth of a second, there is no more apparent intermission of the light
than what occurs during the winking of the eyes.”
“You allude to a very curious fact,” observed the vicar, “that,
although we are perpetually covering the eyeballs with our eyelids, we
are not conscious of the intervals of darkness.”
“The reason of which must surely be obvious from the explanation I have
just offered,” said Mr. Seymour: “the sensation of light is not
exchanged for that of darkness in so short a period as the twinkling of
the eye.”
“I admit the plausibility of your theory,” said the vicar; “but it
appears to me that objects frequently linger on the sight for a longer
period than that which you assign to them. I well remember seeing the
flame of a candle for several seconds after it had been suddenly
withdrawn from the apartment.”
“I admit that strong lights frequently continue for some time thus
visible in the ‘mind’s eye;’ and it is well known that such impressions
are often followed by images of similar shape, but of various colours.
In passing from sunshine to a dark room, we frequently witness the
appearance of stars and circles of vari-coloured light; but this
phenomenon is very distinct from that of the Thaumatrope, and is to be
explained upon very different principles.”[67]
“I know exactly to what you allude,” said the major: “and I do not
doubt but that many of those illusive appearances, which have been
described, might be referred to the operation of the same natural
cause. It is easy to imagine that a person who has steadfastly fixed
his eyes upon an illuminated object, may, for some minutes afterwards,
see the same figure in shade; it was from such a cause, no doubt, that
Constantine saw the image of a cross in the sky. You are, probably,
acquainted with the opinions of Eusebius, Fabricius, and Dr. Lardner,
upon this alleged miracle.”
“Yes,” exclaimed the vicar, “and I also know, that this miracle for the
conversion of Constantine gave origin to the Catholic custom of
illuminating the cross at St. Peter’s in Rome.”
“Sir David Brewster, in his late work on Natural Magic, has given us a
beautiful illustration of the same principle; it is as follows,” said
Mr. Seymour. “A figure dressed in _black_ and mounted upon a _white_
horse, was riding along exposed to the bright rays of the sun, which
through a small opening in the clouds was throwing its light only upon
that part of the landscape. The _black_ figure was projected against a
white cloud, and the white horse shone with particular brilliancy by
its contrast with the dark soil against which it was seen. A person
interested in the arrival of such a stranger, had been for some time
following his movements with intense anxiety; but upon his
disappearance behind a wood, was surprised to observe the spectre of
the mounted stranger in the form of a _white_ rider upon a _black_
steed, and this spectre was seen for some time in the sky, or upon any
pale ground to which the eye was directed.”
“I cannot understand why the spectre should be opposite in colour to
the real image,” observed Tom.
“It is a law of vision which you must for the present take for
granted,” answered his father; “that such is the fact, however,”
continued he, “I will satisfy you by a very simple experiment.”
Mr. Seymour here placed three different coloured wafers in a triangular
form on a piece of white paper, and instructed his son to fix his eyes
steadily upon them for a minute; this having been performed, he next
directed him to turn them from the wafers to a blank part of the paper,
and to tell him what he saw.
“I see,” exclaimed Tom, “three spectral wafers, but the colours are
different; the red wafer is represented by a _green_, the violet by a
_yellow_, and the orange by a _blue_.”
“You now then understand what is meant by the spectral or accidental
colour of a body:--But let us return to the subject of the
Thaumatrope,” said Mr. Seymour.
“Behold!” continued he, “the Trojan ships!”
“Ay, ay, sure enough,” said the vicar; “but let me see, are their forms
according to ancient authority? Very well indeed, Mr. Seymour. Very
well; the poops have the bend so accurately described by Ovid and
Virgil--‘_puppesque recurvæ_,’ as the poet has it. And there is the
triton; but is its size in proportion to the vessel? Yes, sir, you are
doubtless correct, the figure is generally represented of considerable
magnitude on ancient medals; and Silius Italicus, if my memory serves
me, alludes to the weight of the image having on some occasions
contributed to the wreck of the vessel.”
“Spin them round,” said Mr. Seymour.
The vicar complied; exclaiming at the same moment, “‘_Vos ite solutæ.
Ite deæ pelagi._’ They are positively converted into sea-nymphs.
‘_Mirabile monstrum!_’” cried Mr. Twaddleton.
“Here is another classical device; the representation of Eurydice, as
she fell lifeless at the moment Orpheus turned round to gaze on her,”
said Mr. Seymour.
“Charming! charming! I perceive that it is a copy from the splendid
print of Didot in the Paris edition of Virgil.”
“Turn it round, vicar.”
“See! see! she revives, she opens her eyes, and throws her arms around
the neck of her frantic lover: truly, Mr. Seymour, this is a most
interesting toy,” said Mr. Twaddleton.
Mr. Seymour here observed that he had written an epigram to accompany
the subject they had just witnessed, and he trusted that he had given
to it a classical _turn_.
“By all means read it; the subject admits of much classical
decoration,” observed the vicar.
Louisa received the epigram from the hands of her father, and read as
follows:--
“By _turning round_, ’tis said, that Orpheus lost his wife;
Let him _turn round_ again, and she’ll _return_ to life.”
It could not be expected that Mr. Twaddleton should have admired lines
so burdened with puns; but he quietly observed, “I should have
preferred a quotation from the fourth Georgic, so beautifully
descriptive of the fable.”
The next card that was presented for inspection exhibited the
metamorphosis of Daphne into a laurel. As the figure revolved, the
leaves were seen sprouting from her fingers, and her arms lengthening
into branches.
“Come now,” said Mr. Seymour, “let us exhibit the figure which has been
designed at my request: the change which it will undergo during its
revolution may, I trust, on some day be realised; I only regret that it
is not in my power to give the vicar so good a _turn_.”
“Really, if like Crambe, in Martinus Scriblerus, thou hadst a word for
every day in the year, I should certainly say that you were this day
under the dominion of the word _turn_.”
“You know this resemblance?” said Mr. Seymour, as he showed the figure,
painted on one side of the card, to his daughter.
“It is the vicar!” exclaimed Louisa.
It was, indeed, a portrait of that most excellent character,
represented in the costume in which he usually appeared.
“Turn it round,” said Mrs. Seymour.
Louisa twirled the cord, and the effect of the rotation was to convert
the humble vicar into the dignified bishop; his meagre form was
instantly changed into a corpulent figure, which was still farther
inflated by the addition of the episcopal robe and lawn sleeves, while
his angular features were softened by the graceful curves of an immense
wig.
“I will give you a motto for it,” said the major, “and may it be
prophetic!--RAPID PREFERMENT.”
“I will now show you the improvement which has been effected in the
construction and use of this toy,” said Mr. Seymour. “It consists in
altering the axis of rotation while the card is in the act of
revolving, in order that the images on its opposite sides may be
brought in different positions with respect to each other.”
“There cannot be any doubt that such would be the effect, were it
possible to change the axis in the way you propose, but how is this to
be effected?” asked the vicar.
“At first I attempted to produce the change by the addition of several
other strings, but I soon found, that, in order to avail myself of this
expedient, I should be obliged to stop the card before I could alter
the axis, whereas my great object, as I have just stated, was to
produce the change while the card was in the act of spinning,” answered
Mr. Seymour.
“And I shrewdly suspect that such must necessarily be the case, adopt
whatever expedient you may,” observed the major.
“No indeed; I have at length succeeded to my entire satisfaction, and
that too by a most simple scheme, after having tried without success
many very complicated contrivances.”
The party were very desirous of witnessing this triumph of skill, and
Mr. Seymour produced the card, with its appendages, of which we shall
here present our readers with an engraving:--
[Illustration: Fig. 1. Circular card with bottle and another with man’s
torso.]
In all respects the card is constructed like the common Thaumatrope;
the subject, it will be perceived, is that of a man drinking, the
bottle being placed on one side, and the head on the other; upon
revolving the card, in the ordinary manner, the two images will appear
together as represented in:
[Illustration: Fig. 2. Man with bottle halfway to his mouth.]
The improvement consists in inserting in one, or, if a still greater
change be desired, in both sides of the card, two strings, as seen in
Fig. 1; viz. A D and A E, which united at A, form a common string for
twirling the card. The cord A D is elastic, while the string A E is
incapable of being stretched. If, therefore, while the card is in the
act of spinning, the cord A D be pulled with an increased force, it
will take the position D C, while the inelastic string A E will at the
same time assume that of E C. The consequence of which will be that,
instead of the card spinning on an axis in the direction A B, it will
now spin on that which is in the direction C B, and we shall
accordingly see the images on the opposite sides of the card in
different positions, with respect to each other; at one moment the
bottle will be seen in the hand of the drinker as represented in
Fig. 2, and in the next, at his mouth as shown in the cut below:
[Illustration: Fig. 3. Man with bottle at his mouth.]
while, by alternately tightening and relaxing the string, the figure
will be seen in the very act of raising and lowering the bottle.
Mr. Seymour having explained the principle of his improvement as we
have above related, proceeded to exemplify it by a series of different
subjects. We shall select two or three of them for the sake of
illustration. A card with a jockey on one side and a horse on the
other, on spinning round presented the combined figure; upon tightening
the string, in the manner we have described, the card changed its axis,
without the slightest halt or hesitation in its rotation, and the rider
was in an instant canted over the head of his charger; in a moment,
however, he appeared remounted; after which, by pulling the string,
with different degrees of force, he was made to stand on the saddle,
and to exhibit a number of different movements.
The figure of an Indian juggler was represented in the act of throwing
up _two_ balls; on spinning the card, and, at the same time, altering
the position of the circle, in the manner already described, _three_,
and afterwards _four_, became visible. When the card revolved upon its
original axis, two of the balls on the reverse side coincided with the
two painted on the front, so that during the revolution they fell upon
the same spot on the retina, and therefore produced a single
impression; but as soon as the position of the card was changed, these
spots were brought upon different points, and consequently produced
separate and independent images. By alternately tightening and relaxing
the strings, the balls were seen in motion, arising from and falling
into the hand of the juggler.
The next subject which we shall describe produced a considerable degree
of merriment. The vicar inspected the drawing, and observed that he saw
a pulpit placed on the banks of a pond; the card was made to spin, when
a tailor was seen haranguing from the former, and a goose, at the same
instant, fluttering over the water. The circle was now suddenly
shifted, and the vicar was desired to state what he saw:--“Why, bless
me!” exclaimed Mr. Twaddleton, “the tailor is justly served, he is
ducked in the pond, while the goose has taken his place in the pulpit.”
Fearing that we may have exhausted the patience of our reader, we shall
only relate one more example. It was a Turk, who, by means of the
expedient we are illustrating, was made to draw his sabre, and cut off
the head of his antagonist, which immediately fell into the hands of
the decapitated person, who, like St. Denys, appeared as if walking off
with perfect indifference.
“You must admit that these effects are no less novel than they are
extraordinary, and that they are capable of almost endless variation,”
said Mr. Seymour.
“I admit it all,” replied Mr. Twaddleton, “and I have only to express a
hope that, amidst all your improvements, you will never lose sight of
your first and most laudable design, that of rendering your toy
subservient to classical illustration: your triumph will then be
complete, and I shall willingly acknowledge that there is not only
philosophy but literature in your sport.”
“I must not quit this subject,” said Mr. Seymour, “until I have
exhibited another toy, which, like the Thaumatrope, is indebted for its
effect to the optical principle, which I trust is now well understood
by all present, viz. that _an impression made on the retina lasts for a
certain period after the object itself has been withdrawn_.”
The annexed wood-cut represents the instrument to which Mr. Seymour
alluded.
[Illustration: A blackened tin plate with slit, mounted on stand, in
view A; the image of a star as seen, in view B.] It consists of a disc
of blackened tin plate, which is made to revolve on its axis in the
manner above exhibited. A narrow opening extends from the circumference
to the centre as seen at A. If a device of any kind, as a star (which
for increasing the beauty of the experiment ought to be transparent,
and illuminated with a lamp) be placed behind the disc, it is evident
that, as long as the circle remains at rest, no other part of the
figure can be visible than that which is immediately behind the slit A,
but the instant it is put into rapid motion, the whole of the star will
be seen, as exhibited in figure B.
Mr. Seymour observed that the explanation of the phenomenon was
obvious;--each successive portion of the figure seen through the
opening remains on the eye, until the circle has completed its entire
revolution.
“This experiment,” continued Mr. Seymour, “admits of a very curious
modification, which I shall now proceed to exhibit.”
Three coloured wafers were then placed, at equal distances from each
other, on the disc, and the instrument having been arranged before a
looking-glass, the party were desired to observe the reflected image as
the circle revolved.
“The wafers are blended into one continuous zone,” observed Mrs.
Seymour.
“To be sure,” said Louisa; “upon the same principle that the ignited
stick appears as a fiery circle.”
“It would be very strange, after the different experiments we have
seen, if we were not able to explain the present appearance,” observed
Tom.
“The fiery circle produced by the revolving stick is a much better
illustration of the principle; I do not see what object Mr. Seymour has
in thus multiplying his experiments,” said the vicar.
“Gently, if you please, Mr. Twaddleton, and, before you favour us with
your criticism, wait until I have concluded my experiment. You have
seen that the reflected image of the revolving wafers appears as a
continuous zone, and you have very correctly explained the reason of
such an appearance; but I must now request you to inspect the reflected
image through the slit in the disc, as it revolves, and say what new
effect you observe.”
“How very strange!” exclaimed Tom; “I see the three wafers very
distinctly, and perfectly at rest.”
“Impossible,” exclaimed the vicar--“let me have a peep. Why, I declare,
they appear, as you say, stationary, although I know them to be in
rapid motion; as sure as fate I shall become a Cartesian.”
The Major, Louisa, and Mrs. Seymour, were all equally surprised, and
incapable of giving any explanation of the phenomenon they had
witnessed.
“Let us remember,” said Mr. Seymour, “that in viewing the image through
the slit in the revolving disc, we catch but a momentary glance as it
passes before the eye, and that the image thus produced on the retina
is retained until the next revolution again brings the slit into the
same position. Now it is evident, that before the eye can ascertain a
body to be in motion, it must observe it in two successive portions of
time, in order to compare its change of place;[68] but in the
experiment under consideration, the glance is momentary, the wafer is
no sooner seen than it passes away; its figure alone is impressed upon
the retina, and this impression is continued without any change, until
the circle completes its round, and consequently the image must appear
at rest.”
“I understand you; the figure, but not the motion, of the wafer, is
discernible in the short period during which it is visible through the
slit,” observed the vicar.
“I lately witnessed a beautiful illustration of this subject at the
Royal Institution,” said Mr. Seymour. “A number of cogged wheels, cut
out of pasteboard, were set in motion in a perfectly dark room, when
occasional flashes of light from an electric battery, displayed their
forms most distinctly, and yet although whirling round at the time,
they appeared to the spectator as motionless as so many solid blocks of
marble. In like manner, in a storm during the darkness of midnight, the
rolling ship and waves, when rendered visible by flashes of lightning,
will appear as completely at rest, as a representation of them upon the
canvass.[68a] I may at some future time extend this interesting
subject, by exhibiting some optical illusions produced by the
revolution of wheels in different directions, and at different
velocities, for the knowledge[69] of which we are indebted to Mr.
Faraday, and in mentioning that distinguished philosopher,” added Mr.
Seymour, addressing himself more particularly to the vicar, “I cannot
avoid remarking, that if _Philosophy in Sport_ can be made _Science in
Earnest_, the juvenile lectures delivered by that professor have
established the converse proposition, that the sternness of Science may
be relaxed into the engaging aspect of Sport.”
“Before quitting this subject,” continued he, “I have yet another toy
in store for your amusement; it is founded upon the optical principle
which I have every reason to believe you now thoroughly understand.” A
square box was then produced containing a number of card discs, the
edges of which exhibited a series of notches corresponding with the
figures delineated on their margins. That the reader may better
understand their construction, as well as the explanation of Mr.
Seymour, the following representation has been introduced.
[Illustration: As explained above. Figure is a dark-skinned man jumping
in the air.]
“To exhibit the magical effects of this toy,” said Mr. Seymour, “I
will, by means of the spindle to which it is attached, cause it to
revolve rapidly before the looking-glass, and you shall view the
reflection through the openings.”
Each member of the party obeyed in succession the direction thus given,
and severally expressed the great astonishment they felt, at observing
the figures in constant motion, and exhibiting the most grotesque
attitudes.
“Now,” said Mr. Seymour, “attend to my explanation. Each figure is seen
through the aperture, and as it passes and is succeeded in rapid
succession by another and another, differing from the former only in
attitude, the eye is cheated into the belief of its being the same
object successively changing the position of its body. Consider what
takes place in an image on the retina when we actually witness a man in
motion; for instance, a man jumping over a gate, in the first moment he
appears on the ground, in the next his legs are a few inches above it,
in the third they are nearly on a level with the rail, in the fourth he
is above it, and then in the successive moments he is seen descending
as he had previously risen. A precisely similar effect is produced on
the retina, by the successive substitution of figures in corresponding
attitudes, as seen through the orifices of the revolving disc; each
figure remaining on the retina long enough to allow its successor to
take its place without an interval that would destroy the illusion.”
“Nothing can be more satisfactory than your explanation of this very
extraordinary toy,” observed the vicar.
“I am now about to exhibit what I consider a great improvement in its
construction, inasmuch as we thus get rid of the mirror, and enable two
persons to witness the deception at the same time,” said Mr. Seymour.
“For this purpose I have a spindle, at each end of which a disc is
placed, and which I hold in my hand.” We deem it expedient to
illustrate this arrangement by a wood-cut.
[Illustration: Two-sided phantasmascope.]
“By revolving the spindle, you perceive that both cards are made to
turn round with equal velocity. Tom,” said his father, “look through
the orifices of the disc, on my right hand, and Louisa, do the same on
my left.” The children obeyed, and simultaneously expressed their
wonder at what they witnessed. “The figures are all dancing!” cried
Tom; “The horses are all prancing!” exclaimed Louisa.
“You have not yet told us the name of this toy,” observed the vicar.
“It has received several names,” answered Mr. Seymour, “as
_Phantasmascope_, _Phenakistiscope_, &c. derived, as you no doubt
perceive, from the Greek.”
It is scarcely necessary to observe, that the appearances thus produced
may be infinitely varied--heads opening their mouths, and distorting
their countenances; creeping serpents, and machinery in active
operation, are amongst the subjects that have excited the greatest
admiration.
The party now dispersed, not less gratified than they had been
instructed by the lesson of the morning.
* * * * *
The mighty magician of the North has compared the course of a narrative
to the progress of a stone rolled down hill by an idle truant boy,
“which at first moveth slowly, avoiding by inflection every obstacle of
the least importance; but when it has attained its full impulse, and
draws near the conclusion of its career, it smokes and thunders down,
making a rood at every spring, clearing hedge and ditch like a
Yorkshire huntsman, and becoming most furiously rapid in its course
when it is nearest to being consigned to rest for ever: even such,”
says he, “is the course of a narrative; the earlier events are
studiously dwelt upon; but when the story draws near its close, we
hurry over the circumstances, however important, which your imagination
must have forestalled, and leave you to suppose those things which it
would be abusing your patience to relate at length.”
Let the reader of the present work accept this explanation, as an
apology for the abrupt and rapid manner in which we shall now
accelerate our narrative. Since the last lecture, our history has
advanced nearly three weeks, during which interval the major had made
every arrangement for the approaching marriage. It was finally agreed
that the ceremony should be performed at Overton church; and as the
“happy couple” expressed a wish to pass their “honey moon” in a retired
part of Yorkshire, the major consented to postpone his fête until after
their return; nor was he displeased at such an arrangement, as it
afforded time for getting up his entertainment on a more liberal scale
than could otherwise have been accomplished. We shall now avail
ourselves of that peculiar Lethean property which has been often
ascribed to the pen of the author, and commit the reader to the arms of
Morpheus, where it is our intention that he shall remain until the
morning of the nuptials.
* * * * *
* * * * *
Reader, awake! the sun has risen, and Nature is robing herself in her
most gorgeous apparel for the approaching ceremony; the family of the
lodge have been already roused from their slumbers by the attendance of
minstrels, whom the vicar had directed to salute the bridal party at
break of day.----But hark! while we are thus trifling, the village of
Overton is in a bustle; the marriage ceremony is over; the bells of the
church are ringing right merrily their festive peals; many a
handkerchief is waving from the cottage windows, while the doors are
decorated with garlands; the vicarage is ornamented with fragments of
Venetian tapestry; the peasants, dressed in their holiday garments, are
carrying nosegays in their hands, to present to the bride as an
offering of their respect, or to strew in her path, as an emblematic
expression of their wishes.
The party having reached Osterley Park, we were proceeding to
describe the banquet which had been prepared, and the various devices
and emblems with which it had been decorated, under the classical
direction of the vicar, when alas! our publishers, like the harpies
of old, unexpectedly pounced upon us, and warned us from the
feast--“_diripiuntque dapes_,” as Virgil has it.
“You have already exceeded the prescribed limits--you must close the
scene--remember that you have engaged to condense the work into one
volume,” said they. We remonstrate, but in vain. We request but a few
pages, in order that we may give our characters a dramatic exit; but
they reply to us in the words of Sneer, in the Critic, “O never mind!
so as you get them off the stage, I’ll answer for it the _reader_ won’t
care how.”
You see then, gentle reader, how vain it would be to struggle against
such arbitrary and tasteless masters; we shall, therefore, without any
farther apology, ring the manager’s bell, and drop the curtain.
-----
Footnote 63:
The Cartesians maintained that the senses were the great sources of
deception; that everything with which they present us ought to be
suspected as false, or at least dubious, until our reason has
confirmed the report.
Footnote 64:
Ferdinand, Duke of Tuscany, was once struck with the picture of a
child crying; the artist (Peter of Cortona), who was at work upon the
head, wishing to give a proof of his skill, by a few judicious
touches converted the crying into a laughing face. The Duke was in
astonishment; the painter, to show himself master of the human
countenance, restored his first touches, and the Duke again saw the
child weeping.
Footnote 65:
Page 161.
Footnote 66:
Page 49.
Footnote 67:
Those who are desirous of gaining farther information upon this
subject may consult the chapter on “Ocular Spectra, or Accidental
colours,” in Brewster’s Natural Magic, p. 21; and Edinburgh
Encyclopædia, Art. Accidental Colours.
Footnote 68:
“Our knowledge of motion is a deduction of reasoning, not a
perception of sense; it is derived from the comparison of two
positions; the idea of a change of place is the result of that
comparison attained by a short process of reasoning.”--_Lord
Brougham._
Footnote 69:
See Journal of the Royal Institution, No. 2.
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