KALEIDOSCOPE, an instrument which, by means of reflection, enables us to behold an endless variety of beautiful forms of perfect symmetry. It consists of a tube with an eyehole. At the oppo site end chips of colored paper or glass are loosely held in compartments in which by reflection every time that the tube is revolved, and the relative position of the objects in the box altered, a different pattern is observable. The instrument, which was perfected by Sir David Brewster in 1817 (though first invented, under the name of the polyplatin, by Bap tista Porta, in the 16th century) is occa sionally used by designers of patterns for carpets, wall-papers, or calico and other dress materials. It is also useful as a scientific apparatus for illustrating the optical problem of the multiplication of images produced by reflection, when the object is placed between two plane mirrors inclined at different angles. It has likewise been a favorite toy from the year of its invention. Some varieties of the instrument are as follows: (1) Polyangular kaleidoscope: Here the reflecting mirrors are so arranged that their angle of inclination can be altered by screws attached to the outside of the tube at pleasure, and it is in this form that the instrument best illustrates the theory of reflection, and therefore is largely used for scientific instruction.
(2) Polycentral kaleidoscope: FIere more than two mirrors are employed; but not ordinarily more than four. They may be of trapezoidal shape, and form a hollow pyramid, or rectangular, forming a hollow cube. By this means the images produced by reflection of the objects in the box are greatly multiplied and more complicated patterns formed. Dr. Roget was the inventor of this in strument.
(3) Telescopic kaleidoscope: Here the object box is removed and its place taken by a tube capable of being lengthened or shortened by an external screw, and fitted at its end with a double convex lens. The instrument can thus reflect any objects (trees, flowers, etc.) which are brought into its focus. It was in vented by Sir David Brewster.