15. Nor is this the case only with the eye, it is the same with every other sense; precise instances of this kind in regard to the taste, the smell, the touch, &c., will occur plentifully to every one. 16. I consider this solution of the appearances of the colours as perfectly satisfactory. Here it is applied only to one instance, but it is equally applicable to all the rest; and it appears to me to account for all the difficulties which seem to have embarrassed Count Rumford, in his very ingenious and entertaining paper, Phil. Trans. 1794, p. 107. Also in Dr. Priestley's History of Optics, p. 436, there is a curious Chapter, containing the observations of philosophers on blue and green shadows; the true cause of these shadows is not, I think, there mentioned; and it may be entertaining to read that Chapter with these principles in the mind.