Discovery of an Error in the Nautical Almanac. 5^ 



M'as when Mr. Pond first came into office, five or six months 

 before ihe time Dr. Kelly saw him. Therefore, unless Mr. 

 Groombridge's remarks had been accompanied with any ob- 

 servations ot" their importance, it is not difficult to conceive 

 a person, situated as Mr. Pond was in coming into that higU 

 office, forgetting such communications made to him in ge- 

 neral conversation ; and thus I believe the mysterious and 

 delicate question, as Dr. Kelly calls it, may be settled with- 

 out any very great eflorts of conception. 



The paragraph in Dr. Kelly's letter which immediately 

 follows the msinuation, that either Mr, Pond or Mr. Groom- 

 bridge had committed themselves by a representation of a 

 case upon which the plain statement of facts would not 

 bear them out, informs us of a circumstance the most ex- 

 traordinary in his whole letter, and cannot fail to do him 

 great credit in as much as regards his industry -as a calculator 

 and his ability at discovery. I will state the paragraph in 

 his own words : " When I first discovered this error, I 

 made numerous calculations to ascertain its extent." 



Now, notwithstanding Dr. Maskelyne's having stated in 

 the preface to the Nautical Almanac in question, the quan- 

 tity of the obliquity of the ecliptic used in the computation 

 of that epheaifris, and also given the quantity of apparent 

 obliquity deduced from it, which is put down for everv 

 third month throughout the year, o{)posite the first page in 

 the Almanac ; and also given the sun's declination at the 

 two solstices exactly conformable to that obliquity ; yet 

 Dr. Kelly makes numerous calculations to see if it be so 

 or not, as if he could not believe what he saw, and it was 

 necessary for him to make calculations, to know whether the 

 figures he there found did actually represent what they stood 

 for, I take it for granted, that most people any wav con- 

 versant with astronomical calculations, know that the sun'* 

 apparent declination at the two solstices is equal to the ap- 

 parent obliquity of the ecliptic at that time; and if in look- 

 ing over the Nautical Almanac, any doubt had existed in 

 their minds respecting the quantity of the obliquity of the 

 ecliptic, used in the computation of that Almanac, it is na- 

 tural to suppose the first inquiry they would make, would 

 be to know if the sun's declination at the summer and 

 winter solstice corresponded with the obliquity of the 

 ecliptic; and they would therefore compare the apparent 

 obliquity as given opposite the first page of the Almanac, 

 • with the sun's declination at those solstices; bv which they 

 would immediately see whether the obliquity used in the 

 computation of the Almanac corresponded to what had 



been 



