On light. Third course, On the beneficial effects of light, delivered at Aberdeen in November, 1885 / by Gabriel Stokes.

  • Sir George Stokes, 1st Baronet
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: On light. Third course, On the beneficial effects of light, delivered at Aberdeen in November, 1885 / by Gabriel Stokes. Source: Wellcome Collection.

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    all. Some persons are blind from birth, but yet lead tolerably happy lives, receiving it is true much assist- ance from their fellow creatures who are not subject to such a terrible deprivation. We can imagine our- selves accordingly living in a perfectly dark world, destitute of light of any kind, either natural or artificial, guiding ourselves as best might be by the exercise of the senses of touch and hearing. But the absence of light, of that agent of which the excitement of vision is only one of the offices, entails consequences extending far beyond even this. Without a certain amount of warmth, men and animals cannot survive. Now what is the great source of warmth upon earth? Clearly the sun. We use indeed fires in our houses; but even if we could have had these fires independently of the sun, the heat thence derived, taking all the world over, is a mere nothing compared with the heat received directly from the sun. But the sun is separated from the earth by the enormous distance of 92 millions of miles, or thereabouts. How then is this supply of heat con- veyed to us from such an enormous distance ? It is as we familiarly know by radiation; it is therefore to light, in the extended sense in which the word is here used, that we owe this vast supply. Although the power of the sun’s heat is matter of common observation, we are hardly perhaps prepared
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