76 MR. J. SMITH ON THE ORIGIN OF COLOUR 



117. Shall we then call the unit of measure for light red ? 

 If this^ as seems probable, is the case, what then is green 

 or blue? When I come to consider the phenomena of 

 the prism I shall recur to this subject. To speculate, 

 however, on the theory of light, as has been hitherto 

 done — making one supposition to help another, and one 

 emendation to mend another — is a waste of time and of 

 talent. Could such a measure as we are in search of be 

 obtained, it would be of incalculable value to science. 

 Hypothesis is dangerous here. Besides, if these experi- 

 ments are as conclusive as I consider them to be, they 

 prove that the mathematical method of reasoning, so 

 often recommended by Newton in his Optics, has as yet 

 done nothing for the science of colour. But I shall be 

 told, that it is better to have a mathematical equivalent 

 for the value of a ray, even although erroneous, than a 

 mere physical process without one. Well, be it so to 

 those who think so. 



HOEIZONTAL MOTION. 



2nd Class or Expeeiments. 



Transmitted Light, representing Coloured Media. 



118. The light in these experiments was transmitted 

 through open spaces in the figure or disc. 



For the sake of distinction I call the experiments which 

 I am about to describe experiments on transmitted light. 

 In the first class of experiments, when the white of the 



tinctly marked by their colour — one series being blue or green ; the other 

 of a brilliant red, tinged or edged with orange and yellow. In sunlight 

 the colours are more subdued. On rerersing the motion, the two series 

 instantly change colour. This may be considered as another or further 

 analysis of fig. 9, or 8, on a smaller scale. By making rings of various 

 breadths, such as are here shown, to combine, we get a great variety of 

 colour. We may be able, perhaps, to compound any colour in process of 

 time by careful experiment and analysis. 



