respecting Sound and Light. 1 29 



motion the velocity of the corpuscles of light, and thus pro- 

 ducing the fits of transmission and reflection; and even this 

 supposition does not much assist the explanation. It appears, 

 from the accurate analysis of the phenomena which Newton 

 has given, and which has by no means been superseded by 

 any later observations, that the same colour recurs whenever 

 the thickness answers to the terms of an arithmetical progres- 

 sion. Now this is precisely similar to the production of the 

 same sound, by means of an uniform blast, from organ-pipes 

 which are different multiples of the same length. Supposing 

 white light to be a continued impulse or stream of luminous 

 ether, it may be conceived to act on the plates as a blast of air does 

 on the organ-pipes, and to produce vibrations regulated in fre- 

 quency by the length of the lines which are terminated by the 

 two refracting surfaces. It may be objected that, to complete 

 the analogy, there should be tubes, to answer to the organ- 

 pipes : but the tube of an organ-pipe is only necessary to pre- 

 vent the divergence of the impression, and in light there is little 

 or no tendency to diverge ; and indeed, in the case of a resonant , 

 passage, the air is not prevented from becoming sonorous by the 

 liberty of lateral motion. It would seem, that the determination 

 of a portion of the track of a ray of light through any homo- 

 geneous stratum of ether, is sufficient to establish a length as a 

 basis for colorific vibrations. In inflections, the length of the 

 track of a ray of light through the inflecting atmosphere may 

 determine its vibrations : but, in this case, as it is probable that 

 there is a reflection from every part of the surface of the sur- 

 rounding atmosphere, contributing to the appearance of the 

 white line in every direction, in the experiments already men- 

 tioned, so it is possible that there may be some second reflection 

 mdccc. S 



