THEORY OF COLOURS AND SHADOWS. By the Rev. Dr. ISAAC MILNER, F. R. S. DEAN OF CARLISLE, AND PRESIDENT OF QUEEN'S COLLEGE, CAMBRIDGE. SECT.
1. Several years ago, some curious questions concerning the colours of the shadows of bodies, were proposed to me by an ingenious and philosophical friend, who himself can paint very well, and is an excellent judge of colours. He first mentioned the following facts:- 2. Supposing a piece of writing paper to be weakly illumined by white light, and, at the same time, to have a strong red light thrown upon it by any contrivance, the shadow upon the paper, of a body placed in the said red light, will be green. 3. Or, vice versa, if a strong green light be thrown upon the same paper, the shadow of a body placed in the green light will be red. 4. Under similar circumstances, the shadow of a body intercepting orange-coloured light will be blue, purple, or almost violet, according as the orange light contains more or less red; and vice versa. 5. And lastly, the shadow of a body which intercepts yellow light will be purple, and vice versa. 6. The phenomena just mentioned may be exhibited in several ways. The weak white light may always be had in a dark room, either by admitting a small portion of daylight, or by means of a small lamp or wax taper, the light of which is sufficiently white for the purpose; and in regard to the strong coloured lights, they are also easily procured, either by using transmitted or reflected light of the particular colour wanted. As candles and lamps are always at hand, and solar rays not so, I will here briefly describe the method of shewing any one, and, consequently, all, of these beautiful experiments by candle-light.