686 PHILOSOPHICAL TRANSACTIONS. [aNNO I67I. 



them with similar or iincompounded light. For, then they appear of that co- 

 lour only, with which they are illuminated, but yet in one position more vivid 

 and luminous than in another, accordingly as they are disposed more or less to 

 reflect or transmit the incident colour, 



11. From hence also is manifest the reason of an unexpected experiment, 

 which Mr. Hook, somewhere in his micrography, relates to have made with 

 two wedge-like transparent vessels, filled the one with red, the other with a 

 blue liquor : namely, that though they were severally transparent enough, yet 

 both together became opaque ; for, if one transmitted only red, and the other 

 only blue, no rays could pass through both. 



13. I might add more instances of this nature ; but I shall conclude with 

 this general one, that the colours of all natural bodies have no other orgin 

 than this, that they are variously qualified to reflect one sort of light in greater 

 plenty than another. And this I have experimented in a dark room, by illumi- 

 nating those bodies with uncompounded light of divers colours. For, by that 

 means, any body may be made to appear of any colour. They have there no 

 appropriate colour, but ever appear of the colour of the light cast upon them, 

 but yet with this difference, that they are most brisk and vivid in the light of 

 their own day-light colour. Minium appears there of any colour indifFerentlv, 

 with which it is illustrated, but yet most luminous in red; and so bise appears 

 indifferently of any colour with which it is illustrated, but yet most luminous in 

 blue. And therefore minium reflects rays of any colour, but most copiously 

 those indued with red; and consequently when illustrated with daylight, that is, 

 with all sorts of rays promiscuously blended, those qualified with red shall 

 abound most in the reflected light, and by their prevalence cause it to appear of 

 that colour. And for the same reason bise, reflecting blue most copiously, 

 shall appear blue by the excess of those rays in its reflected light ; and the like 

 of other bodies. And that this is the entire and adequate cause of their colours, 

 is manifest, because they have no power to change or alter the colours of any 

 sort of rajs, incident apart, but put on all colours indifferently, with which they 

 are enlightened. 



These things being so, it can be no longer disputed, whether there be colours 

 in the dark, nor whether they be the qualities of the objects we see, no nor 

 perhaps whether light be a body. For since colours are the qualities of light, 

 having its rays for their entire and immediate subject, how can we think those 

 rays qualities also, unless one quality may be the subject of and sustain another; 

 which in effect is to call it substance. We should not know bodies for sub- 

 stances, were it not for their sensible qualities, and the principal of those being 



