56 MR. J. SMITH ON THE ORIGIN OF COLOUR 



83. By means of the experiments to be presently de- 

 scribedj I think that I shall succeed in establishing the 

 following propositions : 



I. That colour can be produced by the motion of a 

 beam of white light without the aid of refraction. 



IT. That to produce colour it is necessary to produce 

 a shadow. 



III. That a ray of light of the same intensity, re- 

 peated at different intervals, gives rise to dif- 

 ferent colours. 



IV. That, taking the intensity of the luminous ether 

 at a given time as the unit, each colour consists 

 in some ratio of the luminous to the non- 

 luminous element, however obtained, and is not 

 a constituent principle of the luminous element 

 itself — that it is not the fraction of an active 

 element, but the ratio of an active to a passive 

 element ; or conversely, 



V. That by reducing or increasing the velocity of the 



machine, or, as we may call it, the ray, and pre- 

 serving the same intervals of light and shade on 

 the diagram, the same effects will be produced 

 as if the ratio between the light and shade had 

 been altered, or as if the light were reflected 

 from a new substance. 



VI. That the refrangibility or reflexibility of a ray 

 does not indicate the colour or quality of a 

 ray. 



VII. That light, or the luminous ether, is conse- 

 quently a simple uncompounded substance. 



VIII. That colour is a compound sensation, or the 

 effect of two coordinate sensations — an active 

 and a passive, a positive and a negative — of 

 motion and no-motion. 



