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An able optician, named Nicol, cut a crystal of Iceland spar in two halves in a certain direction. He polished the severed surfaces, and reunited them by Canada balsam, the surface of union being so inclined to the beam traversing the spar that the ordinary ray, which is the most highly refracted, was totally reflected by the balsam, while the extraordinary ray was permitted to pass on.
But why do I speak thus of a scene which can never fade from my remembrance, but in all future years will glow the brightest picture which nature and civilization have daguerreotyped upon my heart? I rose before the sun, while all the east was glowing with his refracted light.
Cave that this was not in accordance with the laws of optics as he had known them in his younger days. He could understand the rays being refracted by the crystal and coming to a focus in its interior, but this diffusion jarred with his physical conceptions.
Tietkens and I ascended the highest hill in this part of the range. I had yesterday seen something like the top of a ridge south-westerly; I now found it was part of a low distant range, and not of a very promising nature. There was a conspicuous mountain, which now bore north-east about fifty miles away, and I fancied I saw the refracted tops of other ranges floating in the mirage.
I paced about in high wrath, not seeing what I was to do; for to take Roland away, even if he were able to travel, would not settle his agitated mind; and I feared even that a scientific explanation of refracted sound or reverberation, or any other of the easy certainties with which we elder men are silenced, would have very little effect upon the boy.
He discovered that when a ray of light passes through a glass plate, if it strikes the farther surface of the glass at an angle greater than 45 degrees it will be totally refracted instead of passing through into the air.
If a body is either heated or loses its heat when placed in vacuo, he ascribes the conveyance of the heat in both cases "to the vibration of a much subtler medium than air"; and he considers this medium also the medium by which light is refracted and reflected, and by whose vibrations light communicates heat to bodies and is put into fits of easy reflection and transmission.
On the whole, however, neither praise nor blame disquieted him greatly. He was engrossed in the contemplation of Kate Arran's happiness, and basking in the refracted warmth it shed about her. The doctor's prognostications had come true.
He believes, though, that these mysterious radiations are not light, because their behavior is essentially different from that of light rays, even those light rays which are themselves invisible. The Röntgen rays cannot be reflected by reflecting surfaces, concentrated by lenses, or refracted or diffracted.
A whole train of associations connected with the objective world is set going in the mind when rays of light strike the retina refracted from objects. And these associations vary enormously in quantity and value with different individuals; but the one we are here chiefly concerned with is this universal one of touch.
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