COMMETfTATIO ASfRÖNÖMlGi, 167 



« mighl yet have remained in great uncertainiy a* to the parallax of the fixt slars ; as 

 « jou will perceire upon the comparison of the two experiments, 



« Tliis indeed was chiefly owing lo our curions meihber, Mr. George Graham, lo 

 « whöm twe lovers of astronomy ar& also not a liltfe indebted for several other etnet 

 « and well-conlrived instiuments. The necessity of such will scareo be rfisputed by 

 « those Ihat have had any etperience in making aslronotnieal obserrations j and the in- 

 « consislency, which is to be met with among different authors in their attempts to de- 

 « termine small aügle», particularly the annual parallax öf the fix't stars, may be a suf- 

 « ficient proof of it t» otherav Their disagreement iadeed in this arlicle , is not now so 

 K much to be VTöndered at, since I doubl not, but it will appeär very pi-obable, Ihat 

 « ihe inslruments commonly mgde use of by ihem, were üable tö greater errors Ihaa 

 « teany limes that parallax will amouut to. 



« The süccess then of this experiment Cvidently depending very mucb on the accurale- 

 « ness of the Instrument Ihat was principally to be taken care of. In what manner this 

 « was done , is not my present purpose to teil you ; but if from the result of the ob- 

 « servations which I now send you , it shall be judged necessary to commUnicate to 

 « the curious the manner of making Ihem , I may hercaf ler perhaps give them a parti» 

 « cular description, not only of Mr. Molyneux's instrument, but also of my own , 

 « which hath since been erected for the säme purpose and upon the like principlcs, 

 « fhough it is somewhat different in its consluction, for a reason, jou wüt meet with 

 « presently. 



« Mr. Molyneux's apparatns was coftipleated atid fitled for observing about Ihe end 

 « of November 1725 , and on Ihe Ihird day of December following the bright star in Ihe 

 « head of Braco ( marfted y by Bayer ) was for the firsl time observed , as it passed 

 « near the zenilh , and its Situation carefully taken wilh the insti-ument. The like oh- 

 « servations wcre made on the 5*, HA^ and 12* days of the same monlh-, and there 

 « appearing no malerial difference in the place of the star , a farther repetition of Ihem, 

 « at this season seemed neeJless, it being a part of the year, wberein no sensible al- 

 « teration of parallax in this star could soon be expected. It was chiefly therefore cu- 

 « riosity that tempted me (being Ihen at Kew , where Ihe instrument was fixed ) to 

 « prepare for observing the star on December IJ'^, when having adjusted the instrument 

 It, as usual , I pereeived that itpassed a little more souSjiöriy this day>, tlian when it was 

 « observed before, Not suspectrng any olher cause of this appearanee, we first conclu- 

 « ded, that it was owing to Ihe uncertaialy of the observalions, and that either this or 

 « the foregoing were not so exact as we had before supposed ; for which reason we 

 « purposed lo rcpeat the Observation again , in order to determine from whence this 

 « difiereoce proceede4;-aad upon doing it on Decembsr 29''^, I found that the star 



«. pas- 



