Discoveries and inventions of the nineteenth century (1905)
Routledge, Robert · London : G. Routledge and Sons · leaf 517
head of the observer would be interposed between the candleand the eye observed, and the light would then be intercepted. By hold-ing a piece of unsilvered plate glass vertically, we may reflect the light ofa candle into the eye of another person, and then the light thrown outfrom the retinal image… … 466 SIGHT. observer. The positions of the observed and observing eye may be de-scribed as exactly opposite to and near each other, while the candle isplaced to one side in the plane separating the two eyes, and the glass isheld so that it forms an angle of 45° with the line joining the pupils.…
Inventions
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