Salusbury, Thomas
,
Mathematical collections and translations (Tome I)
,
1667
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downwards, and alſo forwards or backwards ten or fifteen fathom,
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keeping it all the while parallel to its ſelf, the viſive ray cannot
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ſtray from the point obſerved in the object, more than thoſe
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teen fathom; and becauſe in a diſtance of eight or ten miles, the
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Inſtrument takes in a much greater ſpace than the Gally or other
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Veſſel kenn'd; therefore that ſmall mutation ſhall not make me
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loſe ſight of her. </
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<
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>The impediment therefore, and the cauſe of
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loſing the object cannot befall us, unleſſe upon the mutation made
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angularly; ſince that
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Teleſcopes
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tranſportation higher or lower, to
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the right, or to the left, by the agitation of the ſhip, cannot import
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any great number of fathomes. </
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<
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>Now ſuppoſe that you had two
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Teleſcopes
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fixed, one at the Partners cloſe by the Deck, and the
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ther at the round top, nay at the main top, or main top-gallant
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top, where you hang forth the
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Pennon
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or ſtreamer, and that they
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be both directed to the Veſſel that is ten miles off, tell me,
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ther you believe that any agitation of the ſhip, & inclination of the
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Maſt, can make greater changes, as to the angle, in the higher tube,
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than in the lower? </
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<
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>One wave ariſing, the prow will make the main
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top give back fifteen or twenty fathom more than the foot of the
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Maſt, and it ſhall carry the upper tube along with it ſo greata ſpace,
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& the lower it may be not a palm; but the angle ſhall change in one
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Inſtrument aſwell as in the other; and likewiſe a ſide-billow ſhall
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bear the higher tube an hundred times as far to the Larboard or
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Starboard, as it will the other below; but the angles change not at
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all, or elſe alter both alike. </
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<
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>But the mutation to the right hand or
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left, forwards or backwards, upwards or downwards, bringeth no
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ſenſible impediment in the kenning of objects remote, though the
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alteration of the angle maketh great change therein; Therefore it
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muſt of neceſſity be confeſſed, that the uſe of the
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Teleſcope
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on the
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round top is no more difficult than upon the Deck at the Partners;
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ſeeing that the angular mutations are alike in both places.</
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<
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>SALV. </
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>How much circumſpection is there to be uſed in affirming
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or denying a propoſition? </
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>I ſay again, thar hearing it reſolutely
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med, that there is a greater motion made on the Maſts top, than at
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its partners, every one will perſwade himſelf, that the uſe of the
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leſcope
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is much more difficult above than below. </
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>And thus alſo I w
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ill excuſe thoſe Philoſophers, who grow impatient and fly out into
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paſſion againſt ſuch as will not grant them, that that Cannon bullet
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which they cleerly ſee to fall in a right line perpendicularly, doth
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abſolutely move in that manner; but will have its motion to be by
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an arch, and alſo very much inclined and tranſverſal: but let us
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leave them in theſe labyrinths, and let us hear the other objections,
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that our Author in hand brings againſt
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Copernicus.
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<
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>SIMP. </
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<
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>The Author goeth on to demonſtrate that in the
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ctrine of
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Copernicus,
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it is requiſite to deny the Senſes, and the </
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