In 1814 Sir David Brewster, while experimenting on the polarization of light, made an invention of the most original and concrete type, which required a high grade of scientific knowledge for its conception and development, but which was not intended for any utilitarian purpose, and yet was of too serious a character to be called a scientific toy. This was his famous kaleidoscope; an instrument described accurately by its name, for it enabled one to see beautiful things. It was very simple in construction and principle, and seems to have fallen short of greatness in only one element, that of usefulness. By a careful adjustment of two prisms at a definite angle to each other, Sir David showed that geometrical images of the utmost beauty and variety could be made of objects placed between the mirrors, especially if those objects were small objects, and if they were of different colors, like bits of colored glass. Knowledge of this escaping, thousands of kaleidoscopes were soon put on the market, and sold in all the principal cities, before Sir David had had time to get a patent. Though the instruments were unscientifically made, they gave beautiful pictures nevertheless; but the result was that the kaleidoscope was not appreciated at its full value. The inventor improved the instrument greatly, and developed it into one of the most beauty-producing appliances known, and one of the most extraordinary and unique. The most remarkable fact connected with it is that no real usefulness for it has ever yet been found. The present author ventures to predict that a clear field of usefulness will some day be found by some fortunate inventor.