The economy of the eyes |
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Pagina 12
... visible with Glasses of moderate Dimen- sions ; the rationale of Telescopes has this in com- mon with other things , that what is most worth learning , is easiest learned ; and is , like many other sciences , reduced to a few clear ...
... visible with Glasses of moderate Dimen- sions ; the rationale of Telescopes has this in com- mon with other things , that what is most worth learning , is easiest learned ; and is , like many other sciences , reduced to a few clear ...
Pagina 33
... visible . ( See Chapter on Double Stars . ) THE 2 FEET is still more superior to the 18 Inch , than that is to the One Foot , both for Terrestrial and Celestial pur- poses ; with this telescope the Celestial objects men- tioned above ...
... visible . ( See Chapter on Double Stars . ) THE 2 FEET is still more superior to the 18 Inch , than that is to the One Foot , both for Terrestrial and Celestial pur- poses ; with this telescope the Celestial objects men- tioned above ...
Pagina 38
... visible.- The eye - glasses are of large diameters , for the purpose of giving a large field of view , and the magnifying power just of sufficient strength to render the object distinguishable . — The object is in- verted , but to those ...
... visible.- The eye - glasses are of large diameters , for the purpose of giving a large field of view , and the magnifying power just of sufficient strength to render the object distinguishable . — The object is in- verted , but to those ...
Pagina 40
... visible in a 5 feet Achromatic , with an aperture of 3 % , are hardly perceivable with a 3 feet , which has an aperture of only 27 - the Illuminating power of the former exceeding that of the latter as 144 does 72.- See the fifth column ...
... visible in a 5 feet Achromatic , with an aperture of 3 % , are hardly perceivable with a 3 feet , which has an aperture of only 27 - the Illuminating power of the former exceeding that of the latter as 144 does 72.- See the fifth column ...
Pagina 54
... visible . " - B . MAR- TIN'S New Elements of Optics , 8vo . 1759 , p . 18 . Mr. Ben Martin's Theory is excellent , but it is not true , -the most probable reason why He could not see as well in the Astronomical Telescope as in the ...
... visible . " - B . MAR- TIN'S New Elements of Optics , 8vo . 1759 , p . 18 . Mr. Ben Martin's Theory is excellent , but it is not true , -the most probable reason why He could not see as well in the Astronomical Telescope as in 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
27ths inches 3ths inches 46 inch aberration Achro Achromatic Telescope adjusted aperture of 3ths appear Astronomical Belts Bootis bright Cassegranian Celestial centre Chapter colour Concave construction Convex Defining power distance distinct distinctly Ditto Dollond Double Stars equal experiments Eye-piece Eye-tube feet Achromatic feet focus feet Newtonian feet Reflector feet Telescope field of view figure Finder fixed stars focal length fying power glass Gregorian Telescope HERSCHEL higher power Huygenian Illuminating power inches aperture inches focus inches in diameter Instrument Jesse Ramsden Jupiter large metal larger lens lenses less light Magnifying power matic mirror Moon Newtonian Reflector Newtonian Telescope object Object-glass observations Opticians Optics pencil of rays perfect perfectly Peter Dollond Phil Planet Pole Star proportion Reader Reflecting Telescopes Rigel Ring of Saturn Satellites scope screw seen shew Sir W. H. Sir Wm small speculum small Star Specula Tele tion tonian Trans tube TULLEY visible vision
Pasaje populare
Pagina 407 - Trace Science, then, with Modesty thy guide ; First strip off all her equipage of Pride ; Deduct what is but Vanity or dress, Or Learning's luxury, or Idleness ; Or tricks to show the stretch of human brain, Mere curious pleasure, or ingenious pain ; Expunge the whole, or lop th...
Pagina 13 - 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 7 - O, it is excellent To have a giant's strength ; but it is tyrannous To use it like a giant.
Pagina 303 - At one time, after sweeping a portion of the heavens with that instrument, he tells us that " the appearance of Sirius announced itself at a great distance like the dawn of the morning, and came on by degrees, increasing in brightness, till this brilliant Star at last entered the field of the telescope with all the splendour of the rising sun, and forced me to take my eye from the beautiful sight.
Pagina 359 - ... and satellites, and eclipsed by them : the most distant of the rings also turning upon its axis, and the same taking place with the farthest of the satellites : all the parts of the system of Saturn occasionally reflecting light to each other: the rings and moons illuminating the nights of the Saturnian : the globe and...
Pagina 238 - Whatever expense an instrument had cost in forming, if it did not fully answer the intended design, he would immediately say, after a little examination of the work, " Bobs, man ! this won't do, we must have at it again:" and then the whole was put aside, and a new instrument begun.
Pagina 384 - I resolved to examine every star in the heavens with the utmost attention and a very high power, that I might collect such materials for this research as would enable me to fix my observations upon those that would best answer my end. The subject has already proved so extensive and still promises so rich a harvest to those who are inclined to be diligent in the pursuit, that I cannot help inviting every lover of astronomy to join with me in observations that must inevitably lead to new discoveries.
Pagina 360 - These rings are at a considerable distance from each other, the smallest being much less in diameter at the outside than the largest is at the inside: the...
Pagina 237 - ... take his seat close to the kitchen fire-side, in order to draw some plan for the forming a new instrument, or scheme for the improvement of one already made. There, with his drawing implements on the table before him, a cat sitting on one side, and a certain portion of bread, butter, and a small mug of porter placed...
Pagina 384 - Herschel was himself the first to point out the discrepancy : — " As soon as I was fully satisfied that in the investigation of parallax the method of double stars would have many advantages above any other, it became necessary to look out for proper stars. This introduced a new series of observation. I resolved to examine every star in the heavens with the utmost attention and a very high power, that I might collect such materials for this research as would enable me to fix my observations upon...