76 Light and Colour. 



of the eye, especially the human eye, has appeared to the 

 writer to be more adapted, taking all points in review, to 

 respond to undulations than corpuscles, or units of matter 

 flying off from a large burning disc, such as the sun. 



Secondly, whether corpuscles from the sun, as a finer 

 polarized form of matter, or undulations, are the real cause 

 of colour, both resolve themselves into matter in one way 

 or the other; for whatever be the initial velocity of any 

 particular kind of rays, the angle upon which they pitch, and the 

 fineness or smallness of that angle, will have much to do in 

 the way in which any particular ray is reflected or 

 absorbed, which latter results in blackness ; whilst other 

 surfaces present a facing, whereby every ray is equally re- 

 flected, and not absorbed hence whiteness, yet the form 

 of ultimate atoms, either as elements, or when combined 

 into given compounds, as gold and chloride of gold, iodine 

 and iodide of potassium, give a special form in their 

 simple or combined state, whereby given rays are well 

 reflected, or rays cross each other and give complementary- 

 hues and colours, or they are imperfectly or partially re- 

 flected, or at such an angle that the reflection meets the 

 eye partially, and hence dulness of lustre or hue, and feebly 

 developed colour ; so that whether special kinds of atoms 

 come from the sun, or special atoms on the earth reflect on 

 the surface rays of undulation from the sun, the result is 

 nearly the same, the stationary matter or atoms upon the 

 earth produce the phenomenon of colour by reflection. 



Thirdly, mordants, having the power to fix colours, could 

 not well do so, and keep them in the figures, etc., in which, 

 as dyes, they are impressed upon cotton or muslin, if they 

 only retained intact a particular mechanical form of sur- 

 face, instead of maintaining a particular chemical com- 

 pound, itself of particular atomic form and composition. 



Fourthly, occasionally blind persons are found to have 



