512 Transactions. — Miscellaneous. 



sence of the rod, only the hand, which feels the strokes when 

 brought within their reach. The vibrations become more 

 rapid, till when they reach the number of thirty-two in a 

 second a deep hum strikes my ear (that is to say, the tympa- 

 num is pressed sixteen times, and sixteen times withdrawn, 

 therefore sixteen blows are received upon the ear). The tone 

 rises continually in pitch, and passes through all the inter- 

 vening grades up to the highest, the shrillest note ; then all 

 sinks again into the former grave-like silence. While full of 

 astonishment at what I have heard, I feel suddenly (by the in- 

 creased velocity of the vibrating-rod) an agreeable warmth, as 

 from a fire, diffusing itself from the spot whence the sound 

 had proceeded. Still all is dark. The vibrations increase in 

 rapidity, and a faint-red light begins to glimmer ; it gradually 

 brightens till the rod assumes a vivid red glow, then it turns 

 to yellow, and changes through the whole range of colours up 

 to violet, when all again is swallowed up in night. Thus 

 nature speaks to the different senses in succession — at first a 

 gentle word, audible only in immediate proximity ; then a 

 louder call from an ever-increasing distance ; till, finally, her 

 voice is borne on the wings of light from regions of immea- 

 surable space.' " 



This passage bears out my idea that light and sound are 

 convertible, the one into the other, through the medium of 

 heat. 



In another place Shellan says, — 



" The gradation of colour from red to ultra-violet is to the 

 eye what the gamut is to the ear, and it is not without reason 

 that we talk of harmony of tone and colour. To the physicist 

 the words ' colour ' and ' tone ' are only different modes of 

 expression for similar and closely-allied phenomena ; they ex- 

 press the perception of regular movements recurring in equal 

 periods of time, in ether producing colours, in air musical 

 sounds, &c." 



In tracing the colours in the spectrum from red to ultra- 

 violet we notice first the three primary colours, red, yellow, 

 and blue. Between red and yellow orange is formed ; between 

 yellow and blue comes green ; and above blue we find violet 

 and ultra-violet, which last seems on the verge of running into 

 the red again, just as the seventh note of the musical scale, or 

 leading note as it is called, seems to want the octave, or repe- 

 tition of the keynote, to follow it — in other words, it suggests 

 it to the ear. 



The colours in the spectrum are arranged as follows : Eed, 

 orange, yellow, green, blue, violet, and ultra-violet (some 

 authorities name the last two indigo and violet). 



Now I come to a very important analogy. If we take the 

 proportion of increase in the number of vibrations in a second 



