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Updated: May 6, 2025
Each man had two anti-gas helmets one with a mica window, and the other with glass eyepieces and a tube through which to breathe out, and which was known later as a P.H. helmet. There were Vermorel Sprayers here and there in the trench, which were entrusted to the care of the sanitary men.
Enough has now, perhaps, been said about the respective properties of object glasses and mirrors, but a word should be added concerning eyepieces. Without a good eyepiece the best telescope will not perform well. The simplest of all eyepieces is a single double-convex lens.
The number of eyepieces purchased with a telescope should never be less than three a very low power say ten to the inch; a very high power, seventy-five or one hundred to the inch, for occasional use; and a medium power say forty to the inch for general use.
Lenses made according to special formulæ, however, and called solid eyepieces, give excellent results, and for high powers are often to be preferred to any other. The eyepieces usually furnished with telescopes are, in their essential principles, compound microscopes, and they are of two descriptions, "positive" and "negative."
William's younger brother Alexander was busy putting up a big lathe in a bedroom, grinding glasses and turning eyepieces; while in the drawing-room itself, sacred to William's aristocratic pupils, a carpenter, sad to relate, was engaged in making a tube and putting up stands for the future telescopes. Sad goings on, indeed, in the family of a respectable music-master and organist!
Next she gave one of the metal-like shields to each of us, bidding us hold them in front of our bodies and heads, and only to look through certain slits in them in which were eyepieces that appeared to be of the same horny stuff as the searchlight window.
If you can afford it, get a full battery of eyepieces six or eight, or a dozen for experience shows that different objects require different powers in order to be best seen, and, moreover, a slight change of power is frequently a great relief to the eye. There is one other thing of great importance to be considered in purchasing a telescope the mounting.
Give me some beer, little fox! The novice obeyed, and a Homeric draught interrupted the interview. Greif turned to Rex, upon whose face the iron eyepieces were being adjusted. All the Swabians present were collected around him, excepting the second, who sat in solitary glory by his beer, opposite the Rhine Korps, awaiting events with stolid indifference.
Through it he scanned slowly and methodically the portion of black heaven that had been assigned to him. The instrument would have resembled a bulky pair of electro-binoculars with its twin tubes and eyepieces, had not there been, underneath the tubes, a small, compact box which by Leithgow-magic revealed the world through infra-red light by one tube, and ultra-violet the other. "Nothing!"
Opticians make glasses with three ranges, and write upon a little bar which shifts their eyepieces, 'Theatre, 'Field, 'Marine. Which of the three is your glass set to? The turn of a button determines its range. You can either look at the things close at hand, or, if you set the eyepiece right and use the strongest, you can see the stars. Which is it to be?
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