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Updated: September 19, 2025
The crystal in question consisted of ..., which, as those who manufactured it for me are aware, admits of being cast with a perfection and equality of structure throughout unattainable with ordinary glass, and wrought to a certainty and accuracy of curvature which the most patient and laborious polishing can hardly give to the lenses even of moderate-sized telescopes, whether made of glass or metal, and is singularly impervious to heat.
Jellico, his torn arm in a sling across his chest, came down-slope from the higher point where he had been using the distance lenses. "We struck straight across and cut off about ten miles by that jungle jog. Now I believe all that I've heard of your people's ability to cross wilderness and not lose their built in 'riding beams, sir.
Its upper surface is paraboloidal in shape, as a spherical surface will not unite in a sharp focus the rays coming from a distant object. The light passes through no glass a great advantage, especially for photography, as the absorption in lenses cuts out much of the blue and violet light, to which photographic plates are most sensitive.
Hence the difficulty the operator sometimes experiences by not being able to "obtain a focus," when he wishes to secure a picture of some very distant objects; he does not get his ground glass near enough to the lenses. Again, the rays from an object near by may be termed diverging rays. This rule is applicable to copying.
In the great class of the Articulata, we may start from an optic nerve simply coated with pigment, the latter sometimes forming a sort of pupil, but destitute of lens or other optical contrivance. With insects it is now known that the numerous facets on the cornea of their great compound eyes form true lenses, and that the cones include curiously modified nervous filaments.
Occasionally he looked at the equestrienne on the prancing roan, but for the greater part of the time the lenses were centered on the face and form of the woman in the buckboard. For the first time in his life Red McVey had dodged a direct issue when Carter had asked him why Douglass had not met them in person.
I got it out, and boiled one of my cameras, but the thing was a failure; it made the wood swell up and burst, and I could not see that the lenses were any better than they were before. I now concluded to boil a guide. It might improve him, it could not impair his usefulness. But I was not allowed to proceed.
They dwelt too far and safe for such pulseless rest. With clarified visions and adjusted lenses these gazed from their high mounts of observation upon "those graves called human existence, not yet resurrected unto life." Esther led the way along a narrow path to an open space, where she and Oswald dismounted. Neither referred to Sir Donald's whim in remaining behind.
The substitution of glass lenses for reflectors is not a new idea, since we find that a proposal to that effect was made by a London optician to Mr. Smeaton, in 1759, for illuminating the Eddystone lighthouse, but was not adopted by him.
But the weight of it closed his lips, and when he opened them again it was to say, "Yes, that is my dream." At once he turned his talk upon the light revolving in their faces; began to explain the lenses and their working in short, direct sentences. She heard his voice, but without following. Pezzack and the under-keeper had drawn apart to the opposite side of the cage and were talking together.
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