370 Astronomical Society. 



pecting that the apparent change of place might be owing to errone- 

 ous observation, it was observed again on the 20th, and he found the 

 star still further south than in the preceding observations. This sen- 

 sible alteration surprised himself and Molyneux, inasmuch as it was 

 the contrary way from which it would have been, had it proceeded 

 from an annual parallax of the star; but being incapable of account- 

 ing for it by want of exactness in the observations, and having no 

 notion of any other cause from which such apparent motion could 

 proceed, they suspected that some change in the materials of the 

 instrument itself might have occasioned it. Under this apprehension 

 they remained some time; but being at length fully convinced, by 

 repeated trials, of the great exactness of the instrument, and finding, 

 by the gradual increase of the star's distance from the pole, that there 

 must be some regular cause which produced it, they examined nicely 

 at the time of each observation how much it was ; and about the 

 beginning of March 1 726, the star was found to be 20" more southerly 

 than at the time of the first observation. It now, indeed, seemed to 

 have arrived at its utmost limit southward ; for in several observations 

 made about this time, no sensible difl^erence could be detected in its 

 situation. By the middle of April it appeared to be returning towards 

 the north, and about the beginning of June it passed at the same 

 distance from the zenith as it had done in December, when it was 

 first observed. From the quick change in the star's declination about 

 this time (it increasing a second in three days) they concluded that 

 it would now proceed northward, as it before had gone southward of 

 Its present situation; and it happened as was conjectured; for it con- 

 tinued to move northward till September following, when it again 

 became stationary, being then near 20" more northerly than in June, 

 and no less than 39" more northerly than it had been in March. 

 From September it returned towards the south, till it arrived, in De- 

 cember, at the very same situation it had been at that time twelve- 

 month, allowing for the difference of declination "on account of the 

 precession of the equinox." 



Such is a brief history of the Kew observations ; commenced, in- 

 deed, for the determination of sensible parallax, but which, as subse- 

 quently in the hands of Herschel, led to a very different result. In 

 reading it, we are at a loss whether most to admire the mode in which 

 the observations were conducted, or the modest unassuming manner 

 in which they are recorded : no possible source of error is allowed to 

 pass without the most rigid examination — no theory suffered to em- 

 barrass the observers in their observations ; the slightest anomaly 

 became the subject of suspicion, till in presumed anomaly was found 

 the most perfect regularity. 



That observations so conducted, leading to results so unexpected, 

 could be abandoned till the law which governed them should be un- 

 folded, was impossible. But Bradley rejected all inquiries into the 

 cause till the effects were accurately determined ; and feeling that the 

 apparent motion was obtained by observations only of one year, — by 

 one instrument, — and by one star, — he erected at VVanstead, aided 

 by his friend Graham, on the 1 9th of August 1 727, his zenith sector 



of 



