light at the surfaces of different media. 225 



will predominate over that of the fluid, and from n io d the 

 force of the fluid will predominate over that of the solid ; so 

 that in such a combination there will be two spheres of reflect- 

 ing activity, one of which begins where the other ends. 



In the case of Fig. 4, where the curves have the same maxi- 

 mum ordinate m 6, we shall have a sphere of reflecting acti- 

 vity commencing at «, reaching its maximum at c, and its 

 minimum at b. 



3. The reflecting forces may be conceived to extend to the 

 same distance, and to vary according to different laws. Two 

 cases of this kind may occur; one, as in Fig. 5, where the 

 maximum of unbalanced force is distant from the surface, and 

 another, as in Fig. 6, where the maximum takes place at the 

 reflecting surface. 



In the conclusions which we have drawn respecting the in- 

 dependence of the reflecting and refracting forces, it was sup- 

 posed that the latter follow the same law in solids and fluids. 

 There seems to be no method of determining whether or not this 

 is the case ; for experiment indicates only the total effect, or 

 the sum of all the ordinates, and these may be compensated, 

 though they vary according to different laws. 



There is one hypothesis, however, on which the preceding 

 experiments may be reconciled with the supposition of the 

 mutual dependence of the reflecting and refracting forces. If 

 we suppose, for example, as in Fig. 3, that the refracting 

 forces of the solid and fluid are regulated by the same curves 

 as their reflecting forces, and that the absolute eff'ect of each 

 is the same; then, though the refractive forces are perfectly 

 balanced, and though the total effect of each reflecting force, 

 taken separately, is the same in the solid as in the fluid, yet 

 light will still be reflected in the manner formerly described. 

 It seems highly probable that the law of the refracting force 

 varies in different bodies ; and if we take for granted the mu- 

 tual dependence of the refracting and reflecting forces, the 

 preceding experiments will establish a variation in the law of 

 the refracting forces of diff'erent media. 



In the undulatory system, the preceding facts may be ex- 

 plained by supposing that the density or elasticity of the ether 

 varies near the surface of diff^grent bodies ; a supposition in 



NEW SERIES. VOL. 1. NO. II. OCT. 1829. P 



