Page:Transactions NZ Institute Volume 25.djvu/656

. LXXIV.—Analogy between Light and Sound: Are they Convertible?

By Miss.

a certain analogy exists between light and sound has long been a recognised fact, and more or less commented on. But that that analogy should be so complete as to argue an affinity between them—nay, more, that it might even be possible to convert the one into the other—this is by no means so generally admitted.

In this idea, which I have long entertained, it would appear that I am not alone, as only a short time ago mention was made in one of the daily papers that Edison purposed making us hear noises in the sun, and this was to be effected by converting the rays forming the spectrum into sound.

It is my purpose to-night to illustrate this idea, first directing your attention to some of the remarkable analogies existing between light and sound, and then translating sound into colour, by what I believe to be a novel process or experiment, using for that purpose coloured glasses.

We know that both light and sound can be converted into heat. We also know that light, sound, and radiant heat are analogous in their laws and conditions. Professor Tyndall remarks upon this in his work upon "Sound." He says, "The action of sound is exactly the same as that of light and radiant heat. They, like sound, are wave-motions; like sound they diffuse themselves in space, diminishing in intensity according to the same law; in fact, every experiment on the refraction of light has its analogue in the refraction of sound."

Does not this alone portray the affinity of light, sound, and radiant heat, and suggest the idea that ultimately they may be found to be but different manifestations of one and the same thing, as we see illustrated by ice, water, and snow?

Let us now briefly consider the way in which light and sound are conveyed to our senses, that we may the better trace their analogy.

Light and sound, as we know, are not substances, but only the vibrations of substances, which vibrations are conveyed to our senses by pulsations through a connecting medium. Light reaches the eye by pulsations through ether, which pervades space; sound reaches the ear by pulsations through atmospheric air.