18 MR. J. SMITH ON THE ORIGIN OF COLOUR 



but no one lias seen these waves or has obtained any proof 

 for their existence. Consequently, it seems to me as use- 

 less to talk of the forms of waves of light as of the forms 

 of waves of gravitation, of the forms of the electric, gal- 

 vanic, or magnetic waves, or of the waves of heat, until 

 something more is knov^n about them. By building a 

 system on hypothesis, we not only bewilder ourselves by 

 making ourselves believe that we are wiser than we are, 

 but we put a drag on science. 



30. I fear I may have introduced this part of the subject 

 too soon, by discussing abstract points before I have de- 

 scribed the experiments which lead to such discussion. This 

 could scarcely, however, have been avoided, for the idea of 

 length of wave is one which meets us at the very threshold 

 of the science, and will continually present itself under va- 

 rious aspects, called forth by the nature of the subject and 

 the processes it involves, so that it will be very difficult to 

 treat of pulsations without supposing the existence of waves 

 of different lengths. And as my principal object is to sub- 

 stitute a new element in the place of the different refran- 

 gibilities of rays, or of the lengths of waves, neither the 

 one nor the other can ever be forgotten or omitted to be 

 put in contrast with the proposed substitute, or the nega- 

 tive element, which is the subject of my inquiries. 



31. So far, then, as my argument has gone, neither the 

 emission nor undulatory theory of light, as they are com- 

 monly taught, can account for such phenomena as are 

 exhibited in my experiments ; it is, therefore, necessary to 

 look for explanations of a much more general character in 

 order to account for such common and every-day appear- 

 ances. 



32. To proceed then with our investigation. The fol- 

 lowing well known experiment, which has received an 

 explanation generally acquiesced in, will help us in the 

 examination of this important subject. 



