Studies in spectrum analysis / by J. Norman Lockyer.

  • Norman Lockyer
Date:
1904
Catalogue details

Licence: In copyright

Credit: Studies in spectrum analysis / by J. Norman Lockyer. Source: Wellcome Collection.

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    fork does for sound. A bell ringing is the equivalent of a fire burning or a star shining. Both with regard to sound and to light there are various kinds of receivers. We can, for instance, by preparing certain surfaces, receive and place on record the shape and length of waves of sound—we can make a sound disturbance per- manent. Photography provides a means of securing a permanent record of light-disturbances. Here we have two receivers, one of sound, the other of light, which give a more or less permanent record. Now I need not say, that as men and women we have ears and eyes, the ear doing for the wave of sound what the eye does for the wave of light. With regard to the medium—always to keep to our phraseology—we have the air, whose function it is to transmit waves of sound : and we have the ether to transmit to us the waves of light. We can imagine a compound sound composed of notes of all possible pitch ; we have an exact equivalent of this in the case of the light in the continuous spectrum, one in which from the red end to the blue or violet end there is no break in the light; like an army going into action there are no vacant places in the line. If we press down first one note of the piano and then another, we get an effect due not to a complete mixture of all possible sounds, but to each sound by Itself Now spectrum analysis depends upon this, that what any one note of a piano which you choose to touch does foi sound, each particle of matter does for light.
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