20 On the ap'parent Changes 



its original breadth, in consequence of the increased sizes of 

 the united drop^. 



, The changes of colour, and of brightness, have not been 

 attentively considered, or happily explained in themselves, or 

 as connected with the other changes of place or of figure. The 

 attempts to account for these are not more philosophical than 

 those of the poet : — 



Ipse Dei clypeus, terrS, cum tollitur im^ 

 Mane rubet, terr^que rubet cum conditur im^. 

 Candidus in summo est ; melior natura quod illic 

 iEtheris est, terraque procul contagia vital. 



Ov. Metamor. lib. 15. 1. 192—5. 



In a continuous medium, a ray of light, passing by the side 

 or edge of any body contained therein, is inflected by the at- 

 traction of the body near which it passes, and bent towards it. 



In such a medium a ray of light passing between two bodies, 

 is inflected and bent by the difference of the forces of the two 

 bodies, towards that body nearest to which it passes, and whose 

 attraction consequently prevails. 



A ray of light so passing, is not only so bent and inflected, 

 but is also dispersed and divided into parts more or less bent 

 in various directions towards the inflecting body, the colours of 

 its several parts being changed, from that of the original light, 

 into rays of what are called prismatic colours, which coloured 

 rays, even in the refractions of the. prism, are produced by in- 

 flections, the blue being nearest to, and most attracted by, the 

 inflecting points, the red most remote from and lest bent to- 

 wards them, the intermediate, in and into intermediate di- 

 rections. 



A ray of light, passing perpendicularly through a series of 

 particles concentrically arranged in the plane of incidence, 

 and at equal distances between the particles, passes on without 

 deviation or bending. 



A ray of light, passing obliquely through a series of particles 

 concentrically arranged in the plane of incidence, will be in- 

 flected and bent, in a direction inclined towards the radius 

 drawn from the centre of arrangement to the point of passage. 



