86 MR. J. SMITH ON THE ORIGIN OF COLOUR 



132. If the edge be removed from the ceutre, there will 

 be less concentration of light when in motion. The edge 

 will have a larger circle of revolution, and we shall now 

 have greens and other allied colours, such as olives of 

 various shades. This indicated something like a system 

 of waves, but attentive consideration of the phenomenon 

 would rather lead to tlie belief that the angle of reflec- 

 tion had some effect, and no doubt it has, in modifying 

 the light, but not in decomposing it, or resolving it into its 

 simple elements. There is not only a different quantity 

 of light reflected from the edge in motion at every angle^ 

 but the circle of revolution is greatly widened, and the 

 ratio of the dark to the light immensely increased. As far as 

 I can perceive, therefore, the very same law is in operation 

 here as in the case of the plane discs — the law of vibra- 

 tions or pulsations, and vibrations or pulsations which can 

 be counted. It must be inferred, however, that if the 

 motion of light is so exceedingly rapid as it is found to 

 be, the length of wave must also be exceedingly large^ 

 otherwise the vibrations would be so frequent as com- 

 pletely to destroy colour, 



133. In conducting experiments by means of perpen- 

 dicular motion, it is not necessary that the figure should 

 have the form of a parallelogram; I only selected the 

 parallelogram as the easiest figure for illustrating the 

 theory and the plan of operation. Any figure may be 

 used, or figures may be cut out of the card, or painted 

 on it, as in the former experiments. Different figures 

 may also be painted on different sides of the card, and a 

 mixture of tints as well as veiy pleasing efl'ects produced 

 in the manner already described. 



134. The number of various figures which maybe made 

 in this way is endless. I will content myself with making 

 a selection of such as will enable us to explain some of the 

 more familiar optical phenomena. 



