Latitudes ofMontjouy and Barcelona. 239 



second supposition, have prevented the adoption of either of 

 these methods of explanation. 



Besides the principal difficulty which has thus remained so 

 long unexplained, there is a second, which though less promi- 

 nent, has not less contributed to throw a doubt over the determi- 

 nation of this important point of the arc of the meridian. It re- 

 gards the latitudes obtained by the star ^ Ursa Majoris, which 

 both at Montjouy and Barcelona are 4" less than those obtained 

 by the other stars. This second anomaly has given rise to as 

 much discussion as the first; its principal cause has indeed 

 been shown, but there is a second cause which, I believe, has 

 also contributed to produce the anomaly, which has not yet 

 been pointed out : thus its solution has remained incomplete 

 to the present day ; as the difference which we have stated to 

 exist between the determinations at Montjouy and Barcelona 

 has also remained unexplained and unaccounted for ; each 

 person, as influenced by disposition, or by the means of infor- 

 mation which he has possessed, attributing the discrepancies to 

 *' errors of observation," or to " anomalies from natural causes." 



A series of astronomical observations, in which I have been 

 engaged for some years past, has led me to examine this sub- 

 ject, so long a mystery to men of science. This series includes 

 certain double stars, amongst which ^ Ursse Majoris is com- 

 prised. Knowing it to be a double star, and recollecting the 

 discussions to which it had given rise, I thought it possible 

 that M. M^chain might not have been aware of this fact, and 

 I accordingly sought what would have been the effect in regard 

 to his observations ; availing myself of the same occasion to 

 recalculate the whole of the latitudes of Montjouy and Bar- 

 celona, with the more exact information which we now possess 

 of the places of the respective stars, and with the additional 

 knowledge, in other respects, which astronomical science has 

 acquired since the time of M. M^chain. 



^ Ursse Majoris is composed of two stars, one of the 3rd, 

 the other of the 6th magnitude, which are 14" apart : the lesser 

 is to the south, and differs from the other in declination from 

 11" to 12". MM. M^chain and Delambre appear to have 

 been unaware of this fact; at least I cannot trace any notice 

 of it, either in their publication respecting the arc of the me- 

 ridian, or in their original manuscripts deposited in the 



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