152' Proceedings of Philosophical Societies. [Ave. 



from the irean are, once + 2S6", once 1-15**, and another time 

 — 2'H". Among the others, the greatest differences do nut amount 

 to a second. .Such is the case with the superior tiausit. Willi 

 respect to the other transit the deviations are greater, namely, 

 + 2-28", + 2-15", + 2-11"; - ] • 3'', - 1'22", the rest do 

 not exceed a second. The mean result is 



For the latitude of the circle 48° 50' 1*5'82" 



For the southern face of the observatory 4S 50 13*16 



From a mean of she observations of MM. "1 .,, r „ IO „ r 



Delarnhre and Mechain J 



we ■■ i ploy the same tables of refraction, 

 e mean declination of the pole star for7 m 10 i^^o 

 rust of January, 1S12 3 



\\ hen we compare it with that which M. Delambre liad esta- 

 blished for 1793 and \J97, M. Maihieii finds th.e lunisolar pre- 

 cision 50.-242" and 50-307" or 50-27,4" by a mean; if we sub- 

 tract from it - 2" for tl tary disturbances, there will remain 

 50-074", The author of the tables of trie sun supposed 50-1" in 

 round numbers. Other astronomers have supposed 50-075". All 

 this agrees as well as can be desired. However, M. Mathieu has 

 not satisfied himself with . : Biot and Arrago, at For- 

 iiieulcra, had 'employed the clot of the pole star to verily 

 their latitudes. M. Mathieu made use of the same means. By a 

 mean between the east and west elongations he has only found 

 0*4 / ", to subtract from the latitude found by th.e transit over the 

 meridian. 1 lence we may suppose 4$° 50' 13*0" for the height of 

 tiie pole at the southern face of the observatory: a kind of mean 

 which however approaches nearer to the transits. 



An inequality «'f 4;95 // between the cast and west elongations 

 furnished him with the means of correcting the right ascension of 

 the pole star. The error of which acted in opposite ways in the 

 two elongations; hence the effect of this error ought to disappear 

 in the sum, but to be double in the difference between the two 

 elongations. To satisfy all these data, we must suppose that the 

 right ascension of the polar star on the 1st of January. 18 12, was 

 0'55 fe 5' 5". Thus, by the mere observation of zenith distances, 

 M. Mathieu lias verified the height of the pole, its declination, and 

 has made a correction upon its right ascension, which appears 

 lit if we consider the slowness with which that star passes over 

 the meridional wire of the telescope. 



The latitude being thus determined, we may with greater confi- 

 dence endeavour to find the solstitial declination of the sun. The 

 excess of the obliquity calculated by the tables, above that which 

 results 



From the winter solstice of 1811, is... + 0-86" 



summer solstice of 1812 + 004 



winter solstice of 1812 + 1-95 



summer solstice of 1813 + O'll 





