304 Facts relating to tha Nautical Almarmc 



window glass in the circles, or glass that is tino-ed* m a 

 slight manner \vitl\ a green or blue colour. The reflection 

 from the glass in the spectacle frame will prevent the defi- 

 ciency from being noticed, or will only give rise to the 

 supposition of the eye being weak. 



[To be continued.] 



LVI. Facts relating to the Nautical Almanac and the 

 Connoissauce des Terns. 



It is well known that the Nautical Almanac has contri- 

 buted more essentially to the improvement of navigation 

 and of practical astronomy in general, than any work of 

 the kind ever published. It was begun in the year 1767, 

 and has been continued up to 1S16 inclusive, making in 

 the whole 50 volumes. 



This most important work was planned, and has been 

 constantly conducted, by tlie Rev. Dr. IN'Iaskelyne, the late 

 Astronomer Royal, whose name mustibr ever stand high in 

 the annals of science, both as a profound mathen)atician 

 and a most accurate and able astronomer; and particu- 

 larly as the founder of the lunar observations, by which thr 

 longitude at sea is now accurately determined; and for 

 this great national purpose the Nautical Almanac was es- 

 tablished. The astronomers of France have since modelled 

 their Connoissauce des Terns on the plan of this publication, 

 and they have been suspected of copying many of its most 

 valuable and laborious calculations, although they pretend 

 that all their articles arc from original computation. A 

 recent discovery, however, seems to remove all doubt on 

 the subject. The Nautical Almanac has been always con- 

 ducted with such accuracy, that there is no instance of any 

 error of importance having been discovered in it. A tri- 

 vial exception, however, has laielv occurred. It has been 

 nhsen'cd that in the volume of the ensuing year, 1812, the 

 obliquity of the ecliptic is assumed about 9 seconds too 

 little, which has probably originated in making adouble cor- 

 rection, in reducing the inean obliquity to the true; which 

 inaccuracy pervades all the columns of the sun's riglit ascen- 

 sion and declination. 



This error was discovered by Dr. Kelly of Finsbury 

 Square, who took an early opportunity of shewing it to 

 Mr. Pond the Astronomer Royal ; and that gentleman, after 

 examining the Almanac, and comparing it with others, 

 agreed as to the existence of the error and the propriety of 

 having it corrected. Dr. Kelly nienlioued it to other sci- 

 entific 



