38(j On the Error discovered in tlie Nautical Almanac. 



great measure on the care with which he discharges his AuXf. 

 Tlie French Connoissarice dcs Terns, whether niodelied or 

 not on the plan of the Nautical Ahnanac, will be allowed to 

 Contain a number of essays on scientific subjects, not onlv 

 original, but of the hiiihest importance to the niatliema- 

 ticiau and astronomer, who has hitherto aKvavs regarded 

 that work as a most valuable acquisition to his library*. 



LXIX. On tlie Error discovered in the Nautical Almanac. 

 By S. Groom BiuDGE, Esq. 



To Mr. Tilloch. 



Sir, In your Magazine for the last month, you have no- 

 ticed the error in the Nautical Almanac for the ensuing 

 year, of the obliquity of the ecliptic, both mean and ap- 

 parent; the quantity of which is 8| seconds. You further 

 irention, that this error was first discovered by Dr. Kelly, 

 of Finsbury Square. Now. I must beg leave to assure you, 

 that is not the fact; having in the early part of the sum- 

 mer 1810 shown the same to Dr. Maskalyne; who replied, 

 that he would examine it, and notice it accordingly. The 

 error is too trivial, to render it necessary to alter the right 

 ascension and declination of the sun, for each day; whicli 

 are the only two parts affected ; the whole of the columns 

 which are used for nautical purposes being calculated inde- 

 pendently of the obliquity of the ecliptic. When Mr. Pond, 

 the present astronomer royal, came into ofBce, I also pointed 

 it out, on my first visit to him ; considering that where the 

 error had originated, was the proper place from whence tu 

 announce tlie correction. 



The greatest equation that is required by the assumption 

 of the obliquity of the ecliptic 8i seconds in error, is only 

 -Jg- of a second in time for the right ascension of the sun; 

 and the whole quantity at the solstices for the declination : 

 the former is not worthy of notice; and the latter may be 

 corrected by a table of the sun's declination, for each de- 

 gree of longitude, with the variation for the differene of 10 



* since the above was written, I have been informed that the French 

 have itated, either in their Coniioissance des Terns or in the New Solar and 

 l>iinar Tables lately published, that they have availed themsclvt-s of the 

 calculations contained in the Nautical Almanac, having occasionally calcu- 

 hued two or three of the first months at the beginning ol" the year, tosatisfy 

 theiTiiclves of the degree of care with vvliich the Nautical Almanac has been 

 coir.pulcd. — T F. 



seconds 



