208 Experimental Philosophy. [Lecture 14. 



duction of the different colours, as the experi- 

 ments with the prism had not yet been made, 

 and it was reserved for Newton to perfect the 

 discovery. 



To begin, however, with the experiment of the 

 former philosopher, let us suppose ourselves in 

 his place. Let A, (PL XVII. fig. 80,) be a glass 

 globe, and ScZ a ray from the sun, and falling 

 on the globe at d ; it will, in that place, suffer a 

 refraction, and instead of going on to c will be 

 bent to n. From n a part of the light will be 

 reflected (for a part will necessarily pass through), 

 and falling obliquely at o, it will again be re- 

 fracted. In this case you see that the globe, 

 from its form, will act in some measure like a 

 prism, ^and the ray will be separated into its 

 component parts. An eye, therefore, situated 

 at g, w 7 ill see the red rays at the line just above 

 the orange, Sec. and so on to the violet. Now 

 you wilf recollect, that in a shower of rain there 

 are drops at all heights, and therefore the eye 

 situated at g will see all the different colours. 



This will account for the first or primary 

 bow, which you see is thus formed by two re- 

 fractions and one reflection; but there is often 

 a second bow on the outside of the other, 

 which is rather fainter, and which is made by 

 two refractions and two reflections. To ex- 

 plain this, take a similar glass globe, B, fig. 81. 

 Let the ray T in that enter at the bottom of the 

 globe at r, where it is refracted, and part of the 



