Chapter XXVI: Appendix

Although I have no doubt that the observations contained in the preceding Chapters are sufficient to satisfy every candid and intelligent person respecting the true nature of all the combinations of plane mirrors that preceded the invention of the Kaleidoscope, yet as there are many who are incapable, from want of optical knowledge, to understand the comparison which has been made between them, I shall here present the opinions of four of the most eminent mathematicians and natural philosophers.

The first of these is contained in a note from the late Professor Wood, Master of St. John’s College, Cambridge, written in reply to a letter, in which I requested him to say, if he had any idea of the effects of the Kaleidoscope when he wrote the thirteenth and fourteenth Propositions of his works on Optics.

“ST. JOHN’S, _May 19, 1818_.
“SIR,—The propositions I have given relating to the
number of images formed by plane reflectors, inclined to
each other, contain merely the mathematical calculation of
their number and arrangement. _The effects produced by
the Kaleidoscope were never in my contemplation._ My
attention has for some years been turned to other subjects,
and I regret that I have not time to read your Optical
Treatise, which I am sure would give me great pleasure.—I
am, Sir, your obedient humble servant,

“J. WOOD.”

The following is the opinion of the late celebrated Mr. James Watt:—

“It has been said here,” says Mr. Watt, “that you
took the idea of the Kaleidoscope from an old book on
gardening. My friend, the Rev. Mr. Corrie, has procured
me a sight of the book. It is Bradley’s Improvements of
Planting and Gardening. London, 1731, Part II. Chap. I.
It consists of two pieces of looking-glass, of equal bigness,
of the figure of a long square, five inches long, and four
inches high, hinged together upon one of the narrow sides,
so as to open and shut like the leaves of a book, which,
being set upon their edges upon a drawing, will show it
multiplied by repeated reflexions. This instrument I have
seen in my father’s possession seventy years ago, and frequently
since, but what has become of it I know not. In
my opinion, the application of the principle is very different
from that of your Kaleidoscope.”

The following is the opinion of the late Mr. Playfair, Professor of Natural Philosophy in the University of Edinburgh:—

“EDINBURGH, _May 11, 1818_.

“I have examined the Kaleidoscope invented by Dr.
Brewster, and compared it with the description of an
instrument which it has been said to resemble, constructed
by Bradley in 1717. I have also compared its effect with
an experiment to which it may be thought to have some
analogy, described by Mr. Wood in his _Optics_, Prop. XIII.
and XIV.

“From both these contrivances, and from every optical
instrument with which I am acquainted, the Kaleidoscope
appears to differ essentially, both in its effect and in the
principles of its construction.

“As to the effect, the thing produced by the Kaleidoscope
is a series of figures presented with the most perfect
symmetry, so as always to compose a whole, in which
nothing is wanting and nothing redundant. It matters not
what the object be to which the instrument is directed; if
it only be in its proper place, the effect just described is
sure to take place, and with an endless variety. In this
respect the Kaleidoscope appears to be quite singular among
optical instruments. Neither the instrument of Bradley,
nor the experiment or theorem in Wood’s book, have any
resemblance to this; they go no further than the multiplication
of the figure.

“Next, as to the principle of construction, Dr. Brewster’s
instrument requires _a particular position of the eye of the
observer, and of the object looked at_, in order to produce its
effect. If either of these is wanting, the symmetry vanishes,
and the figures are irregular and disunited. In the other
two cases, no particular position, either for the eye or the
object, is required.

“For these reasons, Dr. Brewster’s invention seems to
me quite unlike the other two. Indeed, as far as I know,
it is quite singular among optical instruments; and it will
be matter of sincere regret, if any imaginary or vague analogy,
between it and other optical instruments, should be
the means of depriving the Doctor of any part of the reward
to which his skill, ingenuity, and perseverance, entitle him
so well.

“JOHN PLAYFAIR,

_Professor of Natural Philosophy in
the University of Edinburgh_.”

“_P.S._—Granting that there were a resemblance between
the Kaleidoscope and Bradley’s instrument, in any of the
particulars mentioned above, the introduction of coloured
and movable objects, at the end of the reflectors, is quite
peculiar to Dr. Brewster’s instrument. Besides this, a circumstance
highly deserving of attention, is the use of two
lenses and a draw-tube; so that the action of the Kaleidoscope
is extended to objects of all sizes, and at all distances
from the observer, and united, by that means, to the
advantages of the telescope.

“J. P.”

Professor Pictet’s opinion is stated in the following letter:—

“SIR,—Among your friends, I have not been one of the
least painfully affected by the shameful invasion of your
rights as an inventor, which I have been a witness of lately
in London. Not only none of the allegations of the invaders
of your patent, grounded on a pretended similarity
between your Kaleidoscope and Bradley’s instrument, or
such as Wood’s or Harris’s theories might have suggested,
appear to me to have any real foundation; but I can affirm,
that, neither in any of the French, German, or Italian
authors, who, to my knowledge, have treated of optics, nor
in Professor Charles’s justly-celebrated and most complete
collection of optical instruments at Paris, have I read or
seen anything resembling your ingenious apparatus, which,
from its numberless applications, and the pleasure it affords,
and will continue to afford to millions of beholders of its
matchless effects, may be ranked among the most happy
inventions that science ever presented to the lovers of
rational enjoyment.

“M. A. PICTET,
_Professor of Natural Philosophy in
the Academy of Geneva_.”

Those who wish to examine farther the ancient combinations of plane mirrors, and other subjects connected with the Kaleidoscope, are referred to the following works:—

Baptista Porta’s _Magia Naturalis_. Kircher’s _Ars Magna Lucis et Umbræ_. Schottus’s _Magia Universalis Naturæ et Artis_. Bradley’s _Treatise on Planting and Gardening_. Harris’s _Treatise on Optics_. Wood’s _Optics_. Dr. Roget on the _Kaleidoscope_, in the _Annals of Philosophy_, vol. xi. p. 375. _Encyclopædia Britannica_, Art. KALEIDOSCOPE, _by_ Dr. Roget; and the _Compte Rendu des Travaux de L’Académie de Dijon_, pour 1818, pp. 108-117.

Works by SIR DAVID BREWSTER.

MORE WORLDS THAN ONE: the Creed of the Philosopher, the
Hope of the Christian. Cr. 8vo., 4s. 6d.

THE MARTYRS OF SCIENCE: Galileo, Tycho Brahe, and
Kepler. Cr. 8vo., 4s. 6d.

THE KALEIDOSCOPE Practically Described. Cr. 8vo.,
_with Illustrations_, 4s. 6d.

THE STEREOSCOPE Practically Described. Cr. 8vo.,
_with Illustrations_, 4s. 6d.

LONDON:
JOHN CAMDEN HOTTEN, 74, PICCADILLY.