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. [6] See Chapter X. CHAPTER XII. ON THE CONSTRUCTION AND USE OF ANNULAR AND PARALLEL KALEIDOSCOPES. In the instruments already described, the pictures which they create, though they may be made of various outlines, have all a centre to which the reflected images are symmetrically related. The same instruments give an annular pattern, or a pattern returning into itself, and included between two concentric circles, by keeping the objects from the central part of the aperture; but as such a pattern can never have its greatest radius more than the breadth of the mirror, and as annular patterns of a very great radius, where the eye can see only a portion of them at a time, are often required, it becomes of importance to adapt the Kaleidoscope for this species of ornament. [Illustration: FIG. 37.]