18 VETERINARY OPHTHALMOLOGY. 



the red, which it transmits. If any body or thing- 

 reflects all colors, we have white. Should all the colors^ 

 be absorbed, we have black. Light travels 186,000 miles 

 per second (discovered by Roemer in 1676). Scientific- 

 ally this is of great moment, but to us the rate is so 

 great that, for all distances on earth, it is instantaneous. 

 The globe would be girt by a sunbeam quicker than 

 we could wink. The theory of to-day as regards light 

 is the undulatory theory. The earth is supposed to be 

 bathed, embalmed, enveloped by a fluid termed Ether, 

 which is very subtle. Suppose a luminous body sets 

 in motion waves of this Ether which go in every direc- 

 tion, moving, remember, at the rate of 186,000 miles per 

 second. Well, these waves breaking upon the retina 

 cause the molecular disturbance termed " sight." This 

 wave motion is like that of sound, except that the 

 vibrations are transverse — cross-wise. " The sunbeam 

 comes to the earth as simply motions of Ether-waves, 

 yet it is the grand source of beauty and power. Its 

 heat, light and chemical force work everywhere the 

 miracle of life and motion. In the growing plant, the 

 burning coal, the flying bird, the glaring lightning, 

 the blooming flower, the rushing engine, the roaring^ 

 cataract, the pattering rain, we see only varied mani- 

 festations of this one all-energizing force." * 

 * Steele. 



