Fig. 26.
When the light is strong, a circular disk of fine grained white paper may be advantageously placed upon the outer face m o of the object-box.
CHAPTER X.
ON THE CONSTRUCTION AND USE OF
THE TELESCOPIC KALEIDOSCOPE, FOR
VIEWING OBJECTS AT A DISTANCE.
We have already seen, in explaining the principles of the Kaleidoscope, that a symmetrical picture cannot be formed from objects placed at any distance from the instrument. If we take the simple Kaleidoscope, and holding an object-box in contact with the reflectors, gradually withdraw it to a distance, the picture, which is at first perfect in every part, will, at the distance of one-tenth of an inch, begin to be distorted at the centre, from the disunion of the reflected images; the distortion will gradually extend itself to the circumference, and at the distance of eighteen inches, or less, from the reflectors, all the symmetry and beauty of the pattern will disappear. An inexperienced eye may still admire the circular arrangement of the imperfect and dissimilar images; but no person acquainted with the instrument could endure the defects of the picture, even when the slightest distortion only is visible at the centre.
As the power of the Kaleidoscope, therefore, in its simple form, is limited to transparent objects, or to the outline of opaque objects held close to the aperture of the reflectors, it becomes a matter of consequence to extend its power by enabling it to produce perfectly symmetrical patterns from opaque objects, from movable or immovable objects at a distance, or from objects of such a magnitude that they cannot be introduced before the opening of the reflectors. Without such an extension of its power, the Kaleidoscope might only be regarded as an instrument of amusement; but when it is made to embrace objects of all magnitudes, and at all distances, it takes its place as a general philosophical instrument, and becomes of the greatest use in the fine, as well as the useful arts.
Fig. 27.
