Salusbury, Thomas
,
Mathematical collections and translations (Tome I)
,
1667
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all converſion from the Annual motion, could be made, one
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while in a greater, and another while in a leſſer proportion;
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which diverſity, and no other thing, could be aſſigned for the
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cauſe of the alterations, Monethly and Annual, that are ſeen in
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the greatneſſe of the Ebbings and Flowings. </
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<
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>I will now
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ſider how this proportion of the additions and ſubſtractions of
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the Diurnal Revolution, and Annual motion may grow greater
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and leſſer three ſeveral wayes. </
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>One is by increaſing and
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niſhing the velocity of the Annual motion, retaining the
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ons and ſubſtractions made by the Diurnal converſion in the
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ſame greatneſſe, becauſe the Annual motion being about three
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times greater, that is, more velocious than the Diurnal motion
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(conſidered likewiſe in the Grand Circle) if we increaſe it
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anew, the additions and ſubſtractions of the Diurnal motion
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will occaſion leſſe alteration therein: but, on the other ſide,
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making it more ſlow, it will be altered in greater proportion, by
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that ſame diurnal motion, juſt as the adding or ſubſtracting
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four degrees of velocity from one that moveth with twenty
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grees, altereth his courſe leſſe, than thoſe very four degrees would
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do, added or ſubſtracted from one that ſhould move onely with
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ten degrees. </
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>The ſecond way would be, by making the
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ons and ſubſtractions greater and leſſer, retaining the annual
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tion in the ſame velocity; which is as eaſie to be underſtood, as it
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is manifeſt, that a velocity
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v. </
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of 20. degr. </
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<
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>is more altered by the
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addition or ſubſtraction of 10. deg. </
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>than by the addition or
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ction of 4. The third way would be, in caſe theſe two were joyned
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together, diminiſhing the annual motion, & increaſing the diurnal
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additions and ſubſtractions. </
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>Hitherto, as you ſee, it was no
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hard matter to attain, but yet it proved to me very hard to find
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by what means this might be effected in Nature. </
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<
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>Yet in the end,
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I finde that ſhe doth admirably make uſe thereof, and in wayes
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almoſt incredible: I mean, admirable and incredible to us, but
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not to her, who worketh even thoſe very things, which, to our
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capacity, are of infinite wonder, with extraordinary facility and
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ſimplicity: and that which it is hard for us to underſtand, is
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ſie for her to effect. </
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>Now to proceed, having ſhewn that the
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proportion between the additions and ſubſtractions of the
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nal converſion and Annual motion may be made greater and
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ſer, two wayes, (and I ſay two, becauſe the third is comprized in
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the two firſt) I adde, that Nature maketh uſe of them both:
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and farthermore, I ſubjoyn, that if ſhe did make uſe but of one
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alone, it would be neceſſary to take away one of the two
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dical alterations. </
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<
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>That of the Monethly Period would ceaſe, if
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the annual motion ſhould not alter. </
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<
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>And in caſe the additions
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and ſubſtractions of the diurnal revolution ſhould continually </
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