When, by a happy accident, Sir David Brewster had discovered the leading principles of the kaleidoscope while repeating Biot's experiments on the action of fluids upon light, he constructed an instrument in which he fixed permanently, across the ends of the reflectors, pieces of coloured glass, and other irregular objects. But it was not till some time afterwards that the great step towards the completion of the instrument was made, in the idea of giving motion to these objects, which were placed loosely in a cell at the end of the instrument. When this idea was carried into execution, the kaleidoscope in its simple form was completed. The next and by far the most important step of the invention was, to employ a draw tube and lens, by means of which beautiful forms could be created from objects of all sizes, and at all distances from the observer. In this way, the power of the kaleidoscope was indefinitely extended, and every object in nature could be introduced into the picture, in the same manner as if these objects had been reduced in size, and actually placed at the end of the reflector.