Theory of colours and shadows

Having since been led to consider this subject more attentively, 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 enclosed 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 conceptions," so I shall give this theory in his own words.