676 PHILOSOPHICAL TRANSACTIONS. [aNNO I672. 



very subtle, an account may easily be given, why it is reflected and refracted, 

 and why it observes sucli laws in its reflection and refraction as really it does. 



Further, he discourses of colours, and considers how light is changed into 

 colour, sometimes by reflection alone, sometimes by refraction alone, sometimes 

 without either and without the change of the medium, viz. by diffraction. He 

 explains also, how light, by the sole intrinsic modification of itself, passes some- 

 times into a colour that is commonly called apparent; where he declares, that 

 the reason why light passes into an apparent colour, is not some determinate 

 angle at which the rays amongst themselves are inclined, but that that colour is 

 produced by the intention and density of light. He teaches also, that to the 

 vision of things permanently coloured, there are not required any intentional 

 species transmitted from them, and contradistinct from light; but that the light 

 which is diffiised or at least reflected from things coloured, is sufficient; yet 

 with such a modification as is to be found in light apparently coloured, on which 

 occasion many particulars are delivered concerning reflex vision, with an expli- 

 cation of that quaere, how the place of the thing seen is perceived, &c. ? To 

 all which is added, that the modification of light, by which it is both perma- 

 nently, and (as they speak) apparently coloured, or made sensible under the re- 

 presentation of colour, may not improbably be said to be a determinate and 

 most finely furrowed undulation of the same, and a kind of tremulous diffnsion, 

 with a certain very subtle floating, whereby it does, in a peculiar way of appli- 

 cation, aff^ect the organ of vision ; which is illustrated and confirmed by what is 

 by philosophers taught of sound and hearing. Upon which it is inferred, that 

 colours are not any thing permanent in visible things, not of themselves lucid, 

 when they are not illuminated; but that they are the light itself, under some 

 peculiar modification made sensible by the sight. 



Lastly, This first part is ended with a large discourse of the rainbow, its 

 colours and their order, its circular figure, the concentricness of rainbows, &c. 

 Concluding on the whole, that a rainbow, both the primary and secondary, 

 is generated from the solar rays, reflected and refracted by the drops of a rorid 

 cloud, so that the primary is represented by the rays that are once reflected 

 within those drops ; but the secondary, by the rays twice reflected, and which 

 after a double refraction in both cases pass to the eye, placed in the axis of the 

 rainbow. 



The second part is dispatched in six propositions ; in which the author takes 

 pains, notwithstanding all that he has delivered before, to abet Aristotle's 

 opinion, importing, that light is an accident ; though he dissembles not, that 

 that philosopher seems to have somewhere favoured the contrary opinion ; as 

 he also acknowledges, that the experiments and the reasons thence deduced 



