The economy of the eyes |
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Pagina 134
... applied to an Achromatic of 44 inches focus , produces , in the most perfect manner , every intermediate degree of Magnifying power be- tween 100 and 400 , either for Celestial or Ter- restrial uses the Field of Vision continuing ...
... applied to an Achromatic of 44 inches focus , produces , in the most perfect manner , every intermediate degree of Magnifying power be- tween 100 and 400 , either for Celestial or Ter- restrial uses the Field of Vision continuing ...
Pagina 136
... applied to a Telescope with sliding tubes , it is desirable , on account of the great power it produces , that it should have an Adjusting Screw with a tooth and pinion ; these are made separate from the Tele- scope , and introduced ...
... applied to a Telescope with sliding tubes , it is desirable , on account of the great power it produces , that it should have an Adjusting Screw with a tooth and pinion ; these are made separate from the Tele- scope , and introduced ...
Pagina 137
... applied a Pancratic Eye - tube , which gave a power of 70 times , and they de- scribed to me its appearance very accurately . I have seen these two Stars with 230 in an Achromatic Telescope of 28 inches focus , and 2 inches aperture ...
... applied a Pancratic Eye - tube , which gave a power of 70 times , and they de- scribed to me its appearance very accurately . I have seen these two Stars with 230 in an Achromatic Telescope of 28 inches focus , and 2 inches aperture ...
Pagina 150
... applied to those made with another . Whatever may be the cause of the apparent diameter of the Stars , they are certainly not of equal magnitude with the same powers in different Telescopes , nor of proportional mag- nitude with ...
... applied to those made with another . Whatever may be the cause of the apparent diameter of the Stars , they are certainly not of equal magnitude with the same powers in different Telescopes , nor of proportional mag- nitude with ...
Pagina 171
... applied , - an Object Glass of an Inch aperture , will have very nearly as large a field as one of an Inch and a half- but through the larger aperture , Objects will appear twice as bright , as they do through the smaller , the ...
... applied , - an Object Glass of an Inch aperture , will have very nearly as large a field as one of an Inch and a half- but through the larger aperture , Objects will appear twice as bright , as they do through the smaller , the ...
Alte ediții - Afișează-le pe toate
The Economy of the Eyes: Precepts for the Improvement and ..., Partea 1 William Kitchiner Vizualizare completă - 1824 |
Termeni și expresii frecvente
30 inches focus Achromatic Telescope ADAMS on Vision adjust aperture appear Artists assistance become bright Candlelight centre CHAPTER CHARLES BLAGDEN Colour Common Eye concave glass Convex Glasses COOK'S ORACLE degree distance distant objects distinct vision distinctly Dollond Double Stars DRURY LANE THEATRE Ears enable Engraving exactly extremely Eye Glasses Eye-glass Eye-lids fatigued feet field of view focal length give HERSCHEL inch in diameter inches aperture increased injurious Instrument JESSE RAMSDEN Lamp larger less Light look Magnifying power naked Eye Near-sighted Newtonian nifying power Night observed Opera Glass Optician pair of Spectacles Pancratic Eye-tube pencil of rays perfectly Peter Dollond Phil Plate proper proportion Pupil Reader require retina save the King seen seldom Senses sensibility shew Short-sighted Persons Sight Single Object-glass sliding tubes soon Spec Specta Spectacle frame Spectacle Glasses tacles Tele Theatre tion Trans WILLIAM KITCHINER
Pasaje populare
Pagina 21 - Why has not man a microscopic eye ? For this plain reason, man is not a fly.
Pagina 205 - Prescrib'd her heights, and prun'd her tender wing, (Her guide now lost) no more attempts to rise, But in low numbers short excursions tries: Content, if hence, th...
Pagina 199 - And speak, though sure, with seeming diffidence; Some positive persisting fops we know, Who if once wrong will needs be always so; But you with pleasure own your errors past, And make each day a critique on the last.
Pagina 107 - A man of sense sees, hears and retains everything that passes where he is. I desire I may never hear you talk of not minding, nor complain, as most fools do, of a treacherous memory. Mind not only what people say, but how they say it; and if you have any sagacity you may discover more truth by your eyes than by your ears. People can say what they will, but they cannot look just as they will; and their looks frequently discover what their words are calculated to conceal.
Pagina 28 - ... eye than you have been accustomed to do, and desire the aid of plenty of light ; and on looking at a near object, it becomes confused, and appears to have a kind of mist before it, and the letters of a book run one into another, or appear double, &c. ; and BY CANDLELIGHT you catch yourself holding a book &c. close behind the candle.
Pagina 100 - The fact is this, that he does not know a shortsighted person, who has had occasion to increase the depth of his glasses, if he began to use them in the form of spectacles ; whereas he can recollect several instances, where those have been obliged to change their concave glasses repeatedly, for others of higher powers, who had been accustomed to apply them to one eye only.
Pagina 16 - When persons who have long patronized One Eye, and slighted the Other, take to Spectacles, they will (generally) require Glasses of a different focus for each Eye. When You go to an Optician's to choose Spectacles, the first thing to attend to, is to look at a Book with each eye alternately, — and carefully ascertain, if You see equally well, with both Eyes, with the same Glass, at exactly the same distance.
Pagina 130 - Tis but to know how little can be known, To see all others...