4 MR, J. SMITH ON THE ORIGIN OF COLOUR 



that any improvement or progress can be made in our 

 knowledge of the laws of light; for, judging from the 

 past history of science^ human arguments without experi- 

 mental data would lead us farther and farther from a 

 knowledge of divine laws. Besides, who would rashly 

 encounter^ by bare argument, the philosophy of the age; 

 or enter on the study of the prism, without seeking new 

 facts, observations and experiments in defence of a theory 

 opposed to that by means of which so many illustrious 

 investigators explain the facts unfolded by prismatic 

 analysis ? I have therefore ventured on another field, 

 and one, I apprehend, much more easily cultivated by the 

 mass of mankind. In the study of light by means of the 

 phenomena of the prism, although it has engaged the 

 attention of thousands of investigators, we are still met at 

 the very threshold by the question, "What is a prism? 

 Until this question is answered our progress must be 

 very uncertain. If experiment answered the question it 

 would be all well, but the refraction of the rays of light 

 throws no gleam of sunshine on the internal construction 

 of the instrument ; — how then in these circumstances can 

 the prism be considered as an analytical instrument? 

 That it is not such every truly scientific investigator has 

 virtually acknowledged, and still he adopts the inferences 

 derived from its study as the foundation of his inquiries 

 into the physical nature of light. Were the prism an 

 accurate analytical instrument it would leave no doubt on 

 the minds of philosophers as to its indications ; few inqui- 

 rers, however, agree in this respect. Newtou saw seven 

 distinct colours, some have seen only four and others 

 three; and even those who agree as to the number of 

 colours in white light differ as to what the fundamental 

 colours are. Of those who allow only three, one party 

 maintains that the three ar-e Red, Yellow and Blue, another 

 that they are Red, Ch^een and Blue ; a discrepancy which 



