On the North Pular Distances of the jirincipalfxed Stars. 361 



f nd at the same time becoming r.iagnetic^ camiot afterwards 

 be ignited at distances however limited. 



These latter facts show clearly the reason of the anomalous 

 ignition of steel -dure; or, in other vrords, it explains the pheno- 

 menon — that though it may ignite in the first instance, v/e 

 may nevertheless not be able to accomplish it in subsequent 

 attempts ; for the v,'ire in becoming magnetic, becomes also a 

 superior conductor of the caloric superinduced by the galvanic 

 action. 



I have the honour to be, gentlemen, 



Your most obedient and very humble servant, 

 Birmingham, Oct. 8, 1822. J. MuRRAY. 



LXXIV. On the North Polar Distances of the frincipal fixed. 

 Stars, deduced from the Observations iuade at the Ixoycd 

 Observatory at Grecnisicii. 



Our readers may recollect that the catalogue of these stars, 

 inserted in the Nautical Almanac for IS'24-, differed in North 

 Polar Distance so much from the preceding catalogues as to 

 lead to a conclusion that there was some error in the observa- 

 tions : and which was, in a measure, confirmed by a letter of 

 the Astronomer Royal, v/hich v/as read before the Royal So- 

 ciety last year, relative to a derangement in the Mural Circle *. 

 Those differences amounted, in the case oiProcyon, to upv.ards 

 of 9"; and, in the case ox-Sirius, to nearly 7". The catalogue 

 just published, in the Nautical Almanac for 1825, which is 

 deduced aom observations made with the Mural Circle since 

 September 1821, does not wholly remove those doubts: as it 

 still appears to vary very considerably from former obevva- 

 tions. In fact, there seems to be but little difference betv.-ecn 

 the catalogue published in the Nautical Almanac lor 1S2-1-, 

 and that now published in the Nautical Almanac for 1825; as 

 will be seen by the following comparison. And, where the 

 difference is noxo the greatest (as is tb.e case with y Ursa: Ma~ 

 joris), the former ol) iervations almost uniformly agreed with 

 each other. We have too inuch confidence in the excellence 

 and perfection of the Mural Circle, and in the acknowledged 

 accuracy of the Astronomer Royal, Lo believe that these ano- 

 malies will long remain unreconciled or unexplained. 



* See lliis LeUcr in page U5o of our present Number. 

 Vol. GO. No. 295. Nov. 1822. Z z Mean 



