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What fashion it was, did not occur to me at the moment; for the sun, glancing upon the object-glass of the telescope, hindered me from having a fair view. Moreover, my attention was less directed to the dress of the men, than to their movements. The backs of both were towards us; and they were going forward in the same direction as ourselves.
Instruments: 1 sextant, 1 double opera-glass, 1 telescope, 1 box of mathematical instruments, 1 mariner's compass, 1 Fahrenheit thermometer, 1 aneroid barometer, 1 box containing a photographic apparatus, object-glass, plates, chemicals, etc. Clothes: 2 dozen shirts of a peculiar material resembling wool, but evidently of a vegetable origin; 3 dozen stockings of the same material.
Amongst the refracting instruments at work at that period were the glass of the Poulkowa Observatory in Russia, the object-glass of which measured 15 inches in width, that of the French optician Lerebours, furnished with an object-glass equally large, and lastly that of the Cambridge Observatory, furnished with an object-glass 19 inches in diameter.
These generally consist of long bristles, capable of movement and easily excited. In one species examined by me the vibracula were slightly curved and serrated along the outer margin, and all of them on the same polyzoary often moved simultaneously; so that, acting like long oars, they swept a branch rapidly across the object-glass of my microscope.
"But look out, they're coming out of their holes again." I made the object-glass end describe a circle in the air as we slowly backed, and the swordsmen darted away to the shelters they had quitted to follow us as they saw us in retreat.
Newton surmounted this difficulty by laying a double convex lens, the radius of the curvature of each side of which was fifty feet, upon the flat surface of a plano-convex object-glass, and in the way he obtained a plate of air, or of space, varying from the thinnest possible edge at the centre of the object-glass where it touched the plane surface to a considerable thickness at the circumference of the lens.
These telescopes were all made with a convex object-glass and a concave eye-lens, and this type is spoken of as the Galilean telescope. Its defects are that it has no real focus where cross-wires can be placed, and that the field of view is very small. Kepler suggested the convex eye-lens in 1611, and Scheiner claimed to have used one in 1617. But it was Huyghens who really introduced them.
A telescope with this appendage will commonly cost one thousand dollars and upward, so that it is not usually applied to very small ones. We will now suppose that the reader wishes to purchase a telescope or an object-glass for himself, and to be able to judge of its performance.
In certain cases the official guardians and purchasers who are on the look-out take the precaution to disfigure "precious articles" so as to have them bought by their substitutes and accomplices: "for instance, they convert sets of books into odd volumes, and take machines to pieces; the tube and object-glass of a telescope are separated, which pieces the rogues who have bought them cheap know how to put together again."
Here for a moment he placed his valise and parcel on the coping of the stone balustrade, till he had bidden her farewell. Then he turned, and in laying hold of his bag by the dim light pushed the parcel over the parapet. It fell smash upon the paved walk ten or a dozen feet beneath. 'Oh, good heavens! he cried in anguish. 'What? 'My object-glass broken! 'Is it of much value?
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