Kaleidoscope
2 of the 7 encyclopedias on this shelf carry an entry for Kaleidoscope. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
beautiful which, by means of reflection, enables us consists to behold an endless variety of beautiful forms of perfect symmetry. It consists of a tube with an eyehole. At the opposite 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 Baptista Porta, in the 16th century) is occasionally 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: Here more than two mirrors are employed; than four. but not ordinarily more 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 formed. and more complicated patterns for Dr. Roget was the inventor of this instrument. (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 invented by Sir David Brewster. KALEVIPOEG (kä-lā'vē-pög) ("The Son of Kalev"), the national poem of the Esthonians, consisting of 20 cantos of popular songs collected into a continuous epic by Kreutzwald (1857-1859).
Aiton's Encyclopedia (1910)
ka-li'do-skop, an optical toy. The name is from the Greek and signifies a beautiful view. The instrument was invented by Sir David Brewster about 1815. It consists essentially of a brass or paper tube, from four to twelve inches in length, shaped like a telescope. Two strips of mirror nearly as long as the tube are placed within it and cemented together at any angle, as 120 deg, which is a submultiple of 360 deg. At one end of the tube is a small eye hole fitted with clear glass so arranged as to bring the eye as nearly as possible in the plane of both mirrors. The other end of the tube is closed with what is called the object-box. This consists of two disks of glass, one against the end of the mirrors and the other at the end of the tube, the two thus forming a little box or cage in which a number of beads, bits of colored glass, or other diaphanous substances are inclosed. The object-box is just large enough to permit the inclosed objects to change position freely. On looking through the tube these bright objects are seen multiplied as many times as the angle of the reflecting surface, is contained in the whole circumference of a circle. For instance, if the mirrors be placed in the tube at an angle of sixty degrees the figures will appear six times, all symmetrically arranged about a point which is the center of the circle bounded by the tube. The outer glass of the box or cage holding the bits of glass is ground so as to prevent interference of outside objects without obstructing the light. The richer the colored objects, the more beautiful the effect. Tiny glass tubes partially filled with liquid and hermetically sealed, slender threads of twisted glass, bits of netting woven of gold wire,--all produce fine effects. If the tube be twirled slowly the objects shift into new positions and an almost infinite variety of patterns is obtained. In fact, the kaleidoscope is employed to obtain suggestive patterns for decorative work. See Toy