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Having since been led to consider this subject more atten-
tively, in consequence of a conversation with Mr. Wilberforce
concerning a new theory of colours and shadows, I have, through
his intervention, obtained permission to enrich my work with the
following curious remarks: and as Mr. Wilberforce, in his letter
which inclosed them, observes of their reverend and learned
author, that" He is a man unequalled for the store of knowledge
he possesses, for the clearness with which he views, and the
happy perspicuity with which he communicates his concep-
"tions," so i shall give this theory in his -own words.
THEORY OF COLOURS AND SHADOWS,
By the Rev. Dr. MILNER, F. R. S.
DEAN OF CARLISLE, AND PRESIDENT OF QUE-N'S GOLLEGE, 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 g 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.
. , vice vefsA, 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 phnmomena 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