Fig. 22.
The first and most simple method consists in bringing the tube about half an inch beyond the ends of the reflectors. A circular piece of thin plane glass of the same diameter as the tube, is then pushed into the tube, so as to touch the reflectors. The pieces of coloured glass being laid upon this piece of glass when the tube is held in a vertical position, another similar disc of plane glass, having its outer surface ground with fine emery, is next placed above the glass fragments, being prevented from pressing upon them, or approaching too near the first plane glass by a ring of copper or brass; and is kept in its place by burnishing down the end of the tube. The eye being placed at the other end of the instrument, the observer turns the whole round in his hand, and perceives an infinite variety of beautiful figures and patterns, in consequence of the succession of new fragments, which are brought opposite the aperture by their own gravity, and by the rotatory motion of the tube. In this rude state, however, the instrument is by no means susceptible of affording very pleasing exhibitions. A very disagreeable effect is produced by bringing the darkest sectors, or those formed by the greatest number of reflexions, to the upper part of the circular field, and though the variety of patterns will be very great, yet the instrument is limited to the same series of fragments, and cannot be applied to the numerous objects which are perpetually presenting themselves to our notice. These evils can be removed only by adopting the construction shown in [Fig. 22], in which the reflectors reach the very end of the tube. Upon the end of the tube a b, c d, [Fig. 22], is placed a ring of brass, m n, which moves easily upon the tube a b c d, and is kept in its place by a shoulder of brass on each side of it. A brass cell, M N, is then made to slip tightly upon the moveable ring m n, so that when the cell is turned round by means of the milled end at M N, the ring m n may move freely upon the tube. The fragments of coloured glass, etc., are now placed in a small object-box, as it may be called, consisting of two glasses, the innermost of which, m n, is transparent, and the other ground on the outside P, and kept at the distance of ⅛th or ⅒th of an inch by a brass rim: this brass rim generally consists of two pieces, which screw into one another, so that the object-plate can be opened by unscrewing it, and the fragments changed at pleasure. This object-box is placed at the bottom of the cell M N, as shown at O P, and the depth of the cell is such as to allow the side O to touch the end of the reflectors, when the cell is slipped upon the ring m n. When this is done, the instrument is held in one hand with the angular point E, [Fig. 21], downwards, which is known by a mark on the upper side of the tube between a and b, and the cell is turned round with the other hand, so as to present different fragments of the included glass before the aperture A O B. The tube may be directed to the brightest part of the sky in the day-time, or in the evening to a candle, or an Argand Lamp, so as to transmit the light directly through the coloured fragments; but it will always be found to give richer and more brilliant effects if the tube is directed to the window-shutter, a little to one side of the light, or is held to one side of the candle—or, what is still better, between two candles or lamps placed as near each other as possible. In this way the picture created by the instrument is not composed of the harsh tints formed by transmitted light; but of the various reflected and softened colours which are thrown into the tube from the sides and angles of the glass fragments. When the pattern remains fixed in any position of the instrument, a variety of beautiful changes may be effected by making the end of the tube revolve round a candle or a bright gas flame, placed near the object-plate. The general pattern remains the same, but its colours vary both in their position and intensity, as the light falls upon different sides of the fragments of glass.
In the preceding method of applying the objects to the reflectors, the fragments of coloured glass are introduced before the aperture, and pass across it in concentric circles; and as the fragments always descend by their own gravity, the changes in the picture, though infinite in number, constantly take place in a similar manner. This defect may be remedied, and a great degree of variety exhibited in the motion of the fragments, by making the object-plates rectangular instead of circular, and moving them through a groove cut in the cell at M N, in the same manner as is done with the pictures or sliders for the magic lantern and solar microscope. By this means the different fragments that present themselves to the aperture may be made to pass across it in every possible direction, and very interesting effects may be produced by a combination of the rotatory and rectilineal motions of the object-plate. When the object or objects are fixed, and the tube with the reflectors moved round a centre, as described in [Chapter II].,[3] we have the same succession of symmetrical pictures; but in this case every alternate sector is stationary, and the same number in motion, the moving figures always changing their form, and assuming that of the figures in the stationary sectors, which of course change, while the ends of the mirror pass over the fixed objects.
When the simple Kaleidoscope is applied to opaque objects, such as a seal, a watch-chain, the seconds hands of a watch, coins, pictures, gems, shells, flowers, leaves, and petals of plants, impressions from seals, etc., the object, instead of being held between the eye and the light, must be viewed in the same manner as we view objects through a microscope, being always placed as near the instrument as possible, and so as to allow the light to fall freely upon the object. The object-plates, and all transparent objects, may be viewed in this manner; but the most splendid exhibition of this kind is to view minute fragments of coloured glass, and objects with opaque colours, etc., placed in a flat box, the bottom of which is made of mirror-glass. The light reflected from the mirror-glass, and transmitted through the transparent fragments, is combined with the light reflected both from the transparent and opaque fragments, and forms an effect of the finest kind.
As dust is apt to collect in the angle formed by the reflectors, it may be removed when the reflectors are fixed, either by the end of a strong feather, or blown away with a pair of bellows. When the dust is lodged upon the face of the reflectors, it should be removed by a piece of soft leather.
CHAPTER VIII.
ON THE SELECTION OF OBJECTS FOR THE
KALEIDOSCOPE, AND ON THE MODE OF
CONSTRUCTING THE OBJECT-BOX.
Although the Kaleidoscope is capable of creating beautiful forms from the most ugly and shapeless objects, yet the combinations which it presents, when obtained from certain shapes and colours, are so superior to those which it produces from others, that no idea can be formed of the power and effects of the instrument, unless the objects are judiciously selected.