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( 6$4 )
ration of the Declination of Stars of different Lustre ; for that is not sensibly different in Such Stars as Seem rear togetaer, though they appear of very different Magnitudes. And whatever their Situations are (if I proceed according to the foregoing Hypothesis) I find the Same Velocity of Light from my Observations of fmail Stars of the fifth or sixth, as from thofe of the Second and third Magnitude, which in all Probability are placed at very different Distances from us. The fmall Star,for Example, before fpoken of, that is almost opposite to y 'Draconis (being the 3 5tli Camelopard. Hevelii in Mr. Flamfteed’s Catalogue) was 19" more Northerly about the Beginning of March than in September. Whence 1 conclude, according to my Hypothesis, that the Diameter of the little Circle described by a'Star in the Pole of the Ecliptick would be 40", z.
The last Star of the great Bear’s-tail of the id Magnitude (marked » by Bayer) was 3 6" more Southerly about the Middle of January than in July. Hence the Maximum, or greatest Alteration of Declination of a Star in the Pole of the Ecliptick would be 40", 4, exactly the fame as was before found from the Observations of y 'Draconis.
TbeStar of the 5th magnitude in the Head of Perfeus marked r bv Bayer, was ^^|| more Northerly about the End of December than on the 29th os July following. Hence the Maximum would be 41". This Star is not bright enough to be seen as it passes over my Zenith about the End of June, when it should be according to the Hypothesis farthest; South. But because 1 can more certainly depend upon the greatest Alteration of Declination of thofe Stars, which I have frequently observed about the Time? when they become ftatio-a nary.
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nary, with reSpect to the Motion I am now considering ; I will Set down a Sew more Instances of Such, from which you may be able to judge how near it may be possible from these Observations, to determine with what Velocity Light is propagated.
ct Perfei Bayero was 23'' more Northerly at the beginning of January than in July. Hence the Maximum would be 40", 2. «, CaJJiopea was 34'' more Northerly about the End of ‘December than in June, Hence the Maximum would be 40", 8. # 'Draconis was 39" more Northerly in the beginning of Sept cm* her than in March; hence the Maximum would be 40", 2. Capella was about 16'' more Southerly in Augufi than in February; hence the Maximum would be about 40". But this Star being farther from my Zenith than those I have before made use of, I cannot fo well depend upon my Observations of it, as of the others; because I meet with fome fmall Alterations of its Declination that do not seem to proceed from the Caufe I am now considering.
I have compared the Observations of Several other Star?, and they all conSpire to prove that the Maximum is about 40" or 41". I will thereSore SuppoSe that it is 40"# or (which amounts to the Same) that Light move?, or is propagated as far as from the Sun to us in 8' 13". The near Agreement which I met with among my Observations induces me to think, that the Maximum (as I have here fixed *it) cannot differ So much as a Second from the Truth, and therefore it is probable that the Time which Light Spends in passing from the Sun to us, may be determined by thefe Observations within 5" or 10" ; which is fuch a degree of exactnefs nc we can never hope to attain from the Eclipses of s/’ piter's Satellites, F