[ I'iG ] 

 XXVII. Intelligence and Miscellaneous Arlkles, 



DEFENCE OF NAUTICAL ALMANAC. 

 -|- FeT3. 9, 1818. 



Sir, — JUoOKiNG over your valuable Magazine for December 

 last, I was struck with the severe critique on the Commissioners 

 of the Board of Longitude and the Conductors of the Nautical 

 Almanac, in a letter of the 20th of that month, addressed to you 

 from the pen of Astronumicjis. I immediately, at my leisure 

 hours, be<jan computations for the purpose of ascertaining the 

 truth or falsehood of that part of his letter (and to that part 

 only I shall confine my observations) which contains what he 

 supposes corrections of astronomical error* ; and after a very 

 minute investigation,'it affords me no small degree of pleasure 

 and satisfaction in being able to refute and contradict his asser- 

 tions witli the utmost confidence. 



Hejitsf a'^ks why the occultation of Mars in January (1S20) 

 is omitted ? Now, by very accurate calculation^, I find there will 

 be no occultation ; but there will be, as the Nautical Almanac 

 states, a near ai)pulse, and the moon and planet ma?/ apparently 

 be in contact on the northern limb of the moon. He observes, 

 secondly, also, that the true conjunction of Mars will take place 

 iiventy minutes later than is there stated. I shoidd have readily 

 allowed the propriety of this affirmation, provided Mars had at 

 the time, a progressive motion in longitude as well as the moon: 

 this not l)eing the case, however, but, on the contrary, assuming 

 an apparent retrograde one, the two celestial bodies will be in 

 one and the same minute of a degree of the ecliptic, or in con- 

 junction precisely at the time stated, viz. at twenty mimttes 

 past seven o'clock in the morning of the 2d January ; and I 

 would advise Aslronomicus by all means to make himself better 

 acquainted with the subject in general, and, in the last instance, 

 to get a knowledge of the difference between a progressive and 

 appare?it retrograde motion of a p'anet, before he again attempts 

 to bring the Nautical Almanac and its conductors into disre- 

 pute. He again notices with an equal degree of positiveness, 

 that the commencement of the solar eclipse in September is set 

 down full one minute later than it ought to be. But there is no 

 more veracity in this assertion than his former ones, its beginning 

 being September 7, at 0'' 24"^ 11^: and as to the omission of 

 the point ivh^re (not when) the moon makes the first impression 

 on the sun's disc, 49^ 16' (not 48|") from the vertex; it has not 

 been usual to insert it, nor is it, I conceive, of any consequence 

 whatever, otherwise the late or the present Astronomer Royal 

 would, no doubt, have ordered! its insertion. Lastly, he observes 

 that on casting his eye over the configurations of Jupiter's sa- 

 tellites 



