Fig. 36.
A section of the whole of this instrument, in the direction of its length, is shown in [Fig. 33]. A section through M N or O P, near the eye-end, is shown in [Fig. 35], [Fig. 34] representing the mode of supporting the fixed reflector, and [Fig. 36] the mode of supporting the movable reflector. The tube of the Kaleidoscope, in [Fig. 33], is represented by b c d e f g h, and consists of two parts, b c g h, and c d e f g. The first of these parts unscrews from the second, and the second contains all the apparatus for holding and moving the reflectors. At the parts M N O P, of the tube, are inserted a short tube, a section of which is shown in [Fig. 34]. The object of these tubes is to support the fixed mirror A O, which rests with its lower end O upon the piece of brass t. It is kept from falling forwards by the tongue r, connected with the upper part s s, and from falling backward by the piece of cork Q, which may be removed at any time, for the purpose of taking out and cleaning the reflectors. This little tube is fixed to the outer tube by the screws s, s. The contrivance for supporting and moving the second reflector B O, is shown in [Fig. 36], in section; and a longitudinal view of it is given in [Fig. 33]. The mirror B O lies in an opening, cut into two pieces of brass, v B p, one of which is placed at M N, and the other at O P. These two pieces of brass are connected by a rod m n, [Fig. 33]; and in the middle of this rod there is inserted a screw k, which passes through the main tube c d e f g, into a broad milled ring w w, which revolves upon the tube. As the screw k, therefore, fastens the ring w w to the rod m n, the reflector B O will be supported in the tube by the ring w w. The lower part of the mirror B O, or rather of the brass piece v B p, rests at y, upon the piece of watch-spring x y z, fastened to the main tube at z. This spring presses the face of the reflector B O against the ground and straight edge of the other reflector A O, so as always to effect a perfect junction in every part of their length:—The apparatus for both reflectors is shown in [Fig. 35]. An arch of about 45° is cut out of the main tube, so as to permit the screw k to move along it; and hence, by turning the broad ring w w, the reflector B O may be brought nearly to touch the reflector A O, and to be separated from it by an arch of 45°, so as to form every possible angle from nearly 0° to 45°, which is a sufficient range for the Kaleidoscope. The main tube terminates in a small tube at E, upon which may be screwed, when it is required, a brass cap e f, containing a convex lens. A short tube, or cell, a a a a, for containing the object-boxes, slips upon the end of the tube, and should always be moved round from right to left, in order that the motion may not unscrew the portion of the tube b c g h, upon which it moves. When the instrument is used for opaque objects, the end piece, b c g h of the tube, screws off, so as to admit the light freely upon the objects.
The advantages which the Polyangular Kaleidoscopes possess over all others are—
1st, That patterns of any number of sectors, from the simplest to the most complicated, can be easily obtained.
2d, That the reflectors can be set, with the most perfect accuracy, to an even aliquot part of a circle.
3d, That the reflectors can be at any time completely cleaned and freed from all the dust that accumulates between them, and the instrument rendered as perfect as when it came from the hands of the maker.
In order to apply this Kaleidoscope to distant objects, or make it telescopic,[6] a piece of tube with a lens at the end of it is put upon the end piece, b c g h, and may be suited to different distances within a certain range.