touching his Theory of Light and Colours. 203 



through which it passes may not much disturb it; but that 

 suspicion I suppose will vanish by considering, that if at any 

 time the foremost part of an "oblique wave begin to turn it 

 awry, the hindermost part by a contrary action must soon set 

 it straight again. ■ slidue. & dosiz ibidw 



Lastly, because without doubt there are in every transpa- 

 rent body pores of various sizes, and I said that aether stands 

 at the greatest rarily in the smallest pores; hence the aether 

 in every pore should be of a differing rarity, and so light be 

 refracted in its passage out of every pore into the next, which 

 would cause a great confusion, and spoil the body's transpa- 

 rency ; but considering that the aether in all dense bodies is 

 agitated by continual vibrations, and these vibrations cannot 

 be performed without forcing the parts of aether forward and 

 backward from one pore to another by a kind of tremor, so 

 that the aether which one moment is in a great pore, is the 

 next moment forced into a less ; and, on the contrary, this 

 must evenly spread the nether into all the pores not exceeding 

 some certain bigness, suppose the breadth of a vibration, and 

 so make it of an even density throughout the transparent body» 

 agreeable to the middle sort of pores. But where the pores 

 exceed a certain bigness, I suppose the aether suits its den- 

 sity to the bigness of the pore or to the medium within, and 

 so being of a divers density from the aether that surrounds it, 

 refracts, or reflects light in its superficies, and so makes the 

 body where many such interstices are, appear opake. 



Thus much of refraction, reflexion, transparency, and opa- 

 city ; — and now to explain colours. I suppose that as bodies 

 of various sizes, densities, or tensions, do by percussion or 

 other action, excite sounds of various tones, and consequently 

 vibrations in the air of various bignesses ; so, when the rays 

 of light, by impinging on the stiff refracting superficies, excite 

 vibrations in the aether, those rays, whatever they be, as they 

 happen to differ in magnitude, strength, or vigour, excite vi- 

 brations of various bignesses ; the biggest, strongest, or most 

 potent rays, the largest vibrations, and others shorter accord- 

 ing to their bigness, strength, or power; and therefore the ends 

 of the capillamenta of the optic nerve, which front or face the 

 retina, being such refracting superficies, when the rays impinge 

 upon them, they must there excite these vibrations; which 

 vibrations (like those of sound in a trumpet) will run along 

 the aqueous pores or crystalline pith of the capillamenta, 

 through the optic nerves into the sensorium (which light itself 

 cannot do), and these I suppose affect the sense with various 

 colours, according to their bigness and mixture; the biggest 

 with the strongest colours, reds and yellows; the least with 



P2 



