58 MR. J. SMITH ON THE ORIGIN OF COLOUR 



if light and shade should really produce the effects anti- 

 cipatedj even though the experiment should not turn out 

 so satisfactory as to enable me to exhibit any colour I 

 could wish, still, should it even change the tint in the 

 slightest degree, the fact would afford some evidence in 

 favour of my argument. 



87. In want of something better I first of all made a 

 piece of pasteboard into a disc, and coloured the whole 

 black, except a narrow ray radiating from the centre to 

 the circumference, which portion was left white. {See 

 plate IV. fig. 1.) 



I then made the disc revolve on a pivot. The experi- 

 ment was not very encouraging, but it was so far success- 

 ful that, just as the motion was about to stop, or when it 

 was beginning to get slow, I perceived, as I thought, a 

 tinge of brown. I directed the attention of several young 

 persons with good eyes to the appearance, but they did 

 not perceive anything. I was not, however, discouraged 

 by this, as I was aware that it requires some experience 

 of a special kind to observe accurately. From repeating 

 the experiment very often I was more and more convinced 

 of the correctness of my own observations ; and I also 

 arrived at the conviction that, if colour was to be obtained 

 by motion, it must be by having a shiver and more regular 

 motion than I could command with such an instrument. 



This, of course, was merely an introductory experiment 

 previously to getting an apparatus which would give a 

 greater command over the ray of light with which it was 

 intended to operate. 



88. The apparatus which I ordered was of the following 

 construction. {See plate IV. fig. 2.) I call it 



The Chromascope. 



It consists, as will be seen, of one wheel driving another 

 wheel, so as to obtain multiple and steady motion. For 



