202 



by the avilhor 

 at Westbury. 



General cata- 

 logue. 



?7ew correc- 

 tion of the la- 

 titudes from 

 the deviations 

 of observations 



ASTRONOMICAL CIRCLE. 



logue deduced from some observations made at Armagh with 

 a very large equatorial instrument, constriictedby Mr. Trough- 

 ton ; in the third column, are the observations of Mr. Piazzi, 

 of Palermo ; and in the fourth, those made at Westbury. AH 

 the above mentioned observations are arranged in the order of 

 their polar distances, and the positive deviations separated 

 from the negative ; that the cause of error in any of the instru- 

 ments, may be the more easily detected, as likewise any mistake 

 in the assumed latitudes of the respective places of observation. 

 A general catalogue is then added ; whicli is deduced, by 

 taking the mean, generally of the above four 5 but in some 

 places, a few detached observations that I have accidentally 

 procured' of other circular instruments, have been included. 

 The utility of this investigation is not merely confined to the 

 determination of the polar distances of the stars; as, besides 

 this, Rome valuable information on other points may be obtained. 

 In the first place, upon examining the variations that appear 

 in these observations a question naturally occurs, whether, hj 

 changing the assumed latitudes of the respective places of 

 observation, a nearer coincidence might not be obtained ? And 

 I find, that to make the positive deviations equal to the nega- 

 tive, the following corrections should be applied to the co- 

 latitudes J 



+ 1" 



+ r,, 



— ]" 



— 0'',25. 



This method of correcting the latitudes has, I believe, nevCf 

 been employed ; but it seems reasonable to suppose, that, when 

 thus corrected, they will be nearer the truth, than those deter- 

 mined by the usual method : for the same reason, that the de- 

 clinations of the stars resulting from a general comparison, arQ 

 more likely to be accurate, than if deduced from any one single 

 set of observations; but if the Greenwich instrument should 

 be affected with any errors independant of the divisions, in 

 that case, we should be unable to infer any thing decisi%'^e, 

 as to the latitude, by the above method. But from a compa- 

 rison of the observations of y Draconis, observed at Greenwich 

 and Westbury, the latitude of Westbury being previously cor- 

 rected by the above method, I am inclined to believe the 

 latitude of Greenwich requires a very small correction, 



certainly 



Greenwich 

 Armagh 

 Palermo 

 Westbury 



