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tionary, being then near 2,0" more Northerly thau in Juney and no less than 39" more Northerly than it was in March. From September the Star returned towards the South, till it arrived in 'December to the same Situation it was in at that time twelve Months, allowing for the Difference of Declination on account of the Preceflion of the Equinox.
This was a sufficient Proof, that the Instrument had not been the Caufe of this apparent Motion x>i the Star, and to find one adequate to such an Effe<9: seemed a Difficulty. A Nutation of the Earth’s Axis was one of the first rhings that offered itself upon this Occasion, but it was fbon found to be insufficient; for though it might have accounted for the change of Declination in y Draconis yet it would not at the same time agree with the Phsenomena in other Stars; particularly in a finall one almost opposite in right Ascension to y Draconis, at about the fame Distance from the North Pole of the Equator: For, though this Star seemed to move the same way, as a Nutation of the Earth’s Axis would have made it, yet it changing its Declination . but about half as much as y Draconis in the same time ( as appeared upon comparing the Observations of both made upon the same Days, at different Seafons of the Year) this plainly proved, that the apparent Motion of the Stars was not occasioned by a real Nutation, since if that had been the Cause, the Alteration in both Stars would have been near equal.
The great Regularity of the Observations left no room to doubt, but that there was fome regular Cause that produced this unexpe&ed Motion, which did not depend on the Uncertainty or Variety of the
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Seafons of the Year. Upon comparing the Observations with each other, it was discovered, that in both the fore-mentioned Stars, the apparent Difference of Declination from the Maxima, was always nearly proportional to the versed Sine of the Sun’s Distance from the Equino&ial Points. This was an Inducement to think, that the Cause, whatever it was, had fome Relation to the Sun’s Situation with refpe<St to those Points. But not being able to frame any Hypothecs at that Time, sufficient to iblve all the Phenomena, and being very desirous to search a little farther into this Matter; I began to think of erecting an Instrument for my self at Wanjled, that having it always at Hand, I might with the more Ease and Certainty, enquire into the Laws of this new Motion. The Consideration likewise of being able by another Instrument, to confirm the Truth of the Observations hitherto made with Mr. Molyneux's, was no finall Inducement to me; but the Chief of all was, the Opportunity I should thereby have of trying, in what Manner other Stars were affe&ed by the same Cause, whatever it was. For Mr. Molyneux's Instrument being originally designed for observing y ^Draconis (in order, as I said before, to try whether it had any sensible Parallax ) was fb contrived, as to be capable of but little Alteration in its Direction, not above feven or eight Minutes of a Degree : and there being few Stars within half that Distance from the Zenith of Kew, bright enough to be well observed, he could not, with his Instrument, throughly examine how this Cause affetfted Stars differently situated with