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SYDNEY T. KLEIN, F.L.S., F.R.A.S., ON 



edge, a jet of high pressure air is forced through each of the 

 holes successively as they revolve. When the disc does not 

 quite complete one revolution in a second, only fifteen puffs 

 come to the ear in a second of time, and they are heard as 

 puffs ; but when the rate reaches one revolution in a second, the 

 sound, as if by magic, changes into the lowest musical sound. 

 The octave above this is obtained by doubling the number of 

 puffs, namely, by revolving the disc twice in one second, and 

 the next octave by revolving four times in a second, and so on, 

 until at about the thirteenth octave the sound has become so 

 ]iigh that the majority of listeners cannot hear it, and fancy it 

 must have stopped, whereas a few will still be saying, " How 

 shrill it is." At last, at about the fourteenth octave, it passes 

 beyond human audition, and although we can show that the air 

 is still vibrating, all is silent, the ear being incapable of hearing 

 so many beats in a second. It is, however, possible to make 

 these higher vibrations perceptible to our senses. We can 

 actually measure the length of these silent waves, and as we know 

 the rate at which they travel, we can at once comxpute the immber 

 which occur in a second of time and thus ascertain their pitch. 

 We now have to travel only about forty octaves before we arrive 

 at those subtle frequencies which the eye appreciates as light. 

 Beginning with red, the effect transmitted to the brain passes 

 to orange, yellow, green, blue, indigo and violet ; only about one 

 octave that the eye can appreciate, and all is darkness ; but we 

 can still go on a little further by the help of Science. Beyond 

 the violet we have the actinic or chemical rays, which are used 

 in photography, and which enable us to trace the frequencies for 

 a further two octaves. Beyond this we cannot pierce with our 

 present knowledge ; but there may be, and probably are, latent 

 in our nature, senses which, properly developed, will be able to 

 appreciate still more subtle vibrations, and organs which 

 perhaps even now are being prepared for the reception of these 

 subtle influences. Science steadily points to electricity and 

 magnetism being a form of motion, and it may be that in these 

 invisible rays we may some day discover the nature of those 

 mysterious forces. We want, as it were, a special " microscope " 

 to examine these vibrations, which I shall refer to later on, and 

 a similar method to that already mentioned in Space under 

 Celestial Photography, to traverse and examine hundreds or 

 thousands of octaves by each second of exposure ; for although 

 the path extends to infinity, we have already arrived at the 

 utmost limits of our finite senses, and find that after all we can 

 only appreciate, as it were, a few inches along the huge line of 



