On the Error discovered in the Nautical Almanac. 379 



on the declinations of the principal fixed stars, taken with 

 an excellent meridian circular instrument made by Mr. 

 Trnughton, and his comparison ot those observations with 

 a like series ot" observations made with the mural quadrant 

 at Greenwich, pointed out to Dr, Maskelyne a circumstance 

 of which till then he had never even admitted a conjecture, 

 viz. I hat in the course of the number of years in which the 

 mural quadrant at Greenwich had been suspended, it must 

 have changed" its figure. Dr. Maskelyne viewed Mr. Pond's 

 observaiions at first with a very cautious eye ; but havino- sa- 

 tisfied himself that thev were taken with the greatest care 

 and ability, he availed himself of the deductions drawa 

 from them, and occasionally made use of their results, as 

 corrections applied to observations made with the Green- 

 wich quadrant. He brought back the obliquity of the 

 ecliptic to nearly the same quantity he had before adopted; 

 hut whether he ever intended to give a correctioia to the 

 Nautical Alnjanac of 1 8 1 2, or not, 1 am unable to say. It is 

 however likely he did not ihink the difference of sufficient 

 importance to require any thing n)ore than a note, merelv 

 sla.ting what the obliquity of the ecliptic should be : indeed 

 it is uncertain even to the last, whether Dr. Maskelyne was 

 altogether satisfied on this point; for Mr. Groombridtre told 

 nie a long time ago, that he mentioned this circumstance to 

 Dr. Maskelyne, who in reply said he should see by and 

 by; — that he was not sure it was wrong, but if it turned 

 out so, he should correct it. It is worthy here of remark 

 also, that Dr. Maskelyne never readily received notice of 

 any inaccuracies in his deductions. Inaccuracies had been 

 often pointed out to him by various persons, which, upon 

 examination, were generally found to originate in a want of 

 knowledge on their part of the true principles upon which the 

 calculations were founded. A seeming indifference there- 

 fore in the conduct of Dr. Maskelyne was generally re- 

 inarked, and complained of bv persons who gave him such 

 information, in his attention to their statements. 



Haying aheady observed that the mean obliiiuity of the 

 •■cHplic af the beginning- of the year 1812 was given hy Dr. 

 Maskelyne 23° 27' 43'^,3, and that the apparent obliquity 

 was 23" 27' 33",8, differing by f/',.5 from the mean obliquity; 

 ;t appears from the statement in the Philosophical Magazine, 

 that this ditfcrence has led to a conclusion, that ihiT mean 

 •ibliquity had been twice equaled ; and it is curious enough 

 ihat the quantity of mean obliquity as assjgned by Dr. 

 MusUIyne should have been nearly this quantity diflcrent 



from 



