through the axis of the cones and ring as seen in Fig. 31. The other reflector A o, is fixed to an outer ring rr, by

means of an intermediate piece, similar to K G L, the arm F of which, corresponding to G, passes through an annular space or open arch, of more than 90°, cut out of the circumference of the inner ring R R. The arm F is fixed to the outer ring rr by two screws, seen above and below F; and the reflector A o is fixed to the bar corresponding to K L, Fig. 30, by similar screws, for the purpose of adjusting it.

The lower edge o E of the reflector BO E extends about the 15th of an inch below the axis of the cones, as represented by the dotted line in Fig. 30; but the lower edge O E of the other reflector A O E, which is finely ground to an acute angle, forming a perfectly straight and smooth line, is placed exactly in the axis of the cones, so as just to touch a line in the reflector A O E, which coincides with the axis of the cone, and to form a junction with that line in every

part of the two meeting planes. The very nice adjustments which are necessary to produce so exact a motion are effected by the screws corresponding to K and L.

If we now fix the outer ring rr into the ring of a stand S T, so as to be held fast, and turn the cones with the hand, we shall give motion to the reflector B O, so as to place it at any angle we please, from 0° to 90°; and during its motion through this arch, the junction of the two reflectors must remain perfect, if the touching lines are adjusted, as we have described them, to the axis of motion, which must also be the axis of the cones and rings. If, on the contrary, we take away the stand, and, holding the instrument in the hand by either of the cones M, N, turn the ring R R with the other, we shall give motion to its reflector a o, and produce a variation in the angle in the same manner as before. The same effect may be produced by an endless screw working in teeth, cut upon the circumference of the outer ring r r.

In order to enable the observer to set the reflectors at once to any even aliquot part of a circle, or so as to give any number of pairs of direct and inverted images, the most convenient of the even aliquot parts of the circle are engraven upon the ring rr; so that we have only to set the index to any of these parts, to the number 12, for example, and the reflectors will then be placed at an angle of 30° (12 × 30 = 360°), and will form a circular field with twelve luminous sectors, or a star with six points, and consequently a pattern composed of six pairs of direct and inverted images.

As the length of the plates is only about five inches, it is necessary, excepting for persons very short-sighted, to

have a convex lens placed in front of the eye-hole E, as shown in Figs. 30 and 32. A brass ring containing a plane glass screws into the outer ring c D, when the instrument is not in use; and there is an object-box containing fragments of differently coloured glass. This object-box consists of two plates of glass, one ground and the other transparent, set in brass rims. The transparent one goes nearest the reflector, and the brass rim which contains it screws into the other, so as to enclose between them the coloured fragments, and regular figures of coloured and twisted glass. A loose ring surrounds this object-box; and when this ring is screwed into the circular rim C D, the object-box can be turned round so as to produce a variety of patterns, without any risk of its being detached from the outer cone.

In applying this instrument to opaque objects, such as engravings, coins, gems, or fragments of coloured glass laid upon a mirror, the aperture of the mirrors is laid directly over them, the large cone м м having been previously unscrewed, for the purpose of allowing the light to fall freely upon the objects. This property of the Kaleidoscope is of great importance, as in every other form of the instrument opaque objects must be held obliquely, and therefore at such a distance from the reflectors as must affect the symmetry of the pattern.

As the perfection of the figures depends on the reflectors being kept completely free of dust, particularly at their junction, where it naturally accumulates, the greatest facility is given by the preceding construction in keeping them clean. For this purpose, the large cone must be unscrewed; the reflectors having been previously closed, by turning the index to 60 on the ring. They are next to be opened to the utmost,

and the dust may in general be removed by means of a fine point wrapped in clean and dry wash-leather. If any dust, however, still adheres, the small screw in the side of the ring opposite to the index should be removed, and the smaller cone, N N, also unscrewed. By easing the supporting screws of either of the reflectors, their touching sides will separate, so as to allow a piece of dry wash-leather to be drawn between them. When every particle of dust has been thus removed, the metals should be re-adjusted and closed before the cones are replaced; both of which should be screwed firmly into the ring R R.

As the axis of motion in the preceding construction is necessarily the axis of the cones and rings, the diameter of these cones and rings must everywhere be double the breadth of the reflectors. From this cause, the tube, and consequently the object-box, are wide, and the instrument is, to a certain degree, not very portable. This defect is completely avoided in another Polyangular Kaleidoscope constructed by Mr. Bate, upon entirely different principles, which we shall now proceed to describe.

Bate's Polyangular Kaleidoscope with Glass Reflectors.

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 bcdefgh, 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 ss, and from falling backward by the