110 THE EEASON WHY. 



" The light of the body is the eye : if therefore thine eye be single, thy whole 

 body shall be full of light." MATT, v 



upon the eye which makes the object that directs the vibrations 

 appear red. Yellow light requires 44,000 vibrations in an inch, 

 and 535,000,000,000,000 in a second of time. And the other 

 colours enumerated (see 464) all require different velocities of 

 vibration to produce the colours by which they are distinguished. 



Accepting the theory of vibrations, and applying it to the elucidation of the 

 phenomena of light it is unnecessary, we think, to believe that a ray of white 

 light contains rays in a state of colour. It is said that if we divide a circular 

 surface into parts, and paint the various colours in the order and propor- 

 tions in which they occur in the refracted ray, and then spin the circle with 

 great velocity, the colours will blend and appear white. But such is not the 

 case ; the result is in some degree an illusion, arising out of the sudden removal 

 of the impression made upon the eye by the colours , and if a piece of white 

 paper be held by the side of the coloured circle in motion, the latter will be 

 found to be grey. "When it is remembered that in colouring a white surface 

 with thin colours, the white materially qualifies the colours, it must be admitted 

 that the experiment fails to support the assertion that the colours of the 

 spectrum produce white. But there can be no difficulty in understanding that 

 a ray of light undergoing refraction, becomes divided into minor rays, which 

 differing in their degrees of refrangibility, vary also in the velocity of tJieir 

 vibrations, and produce the several sensations of colour. 



466. Tfr Tiy is a substance white ? 



Because it reflects the light that falls upon it without altering 

 its vibrations. 



467. Why is a substance black ? 



Because it absorbs the light and puts an end to the vibrations. 



468. Why is the rose red ? 



Because it imparts to the light that falls upon it that change 

 in its vibratory condition, which produces on our eyes the 

 sensation of redness. 



469. Why is the lily white ? 



Because it reflects the light without altering its vibrations. 



470. Whii is the primrose vellow ? 



J JL / 



Because, though it receives white light, it alters its vibrations to 

 44,000 in an inch, and 535,000,000,000,000 in a second, and this is 

 the velocity of vibration which produces upon the eye a sensation 

 oi yellow. 



