“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.