339 



Art. XV. ASTRONOMICAL AND NAUTICAL 



COLLECTIONS. 



No. XX. 



i. Example of the Correction of a Lunar Distance, computed by 



means of Mr. David Thomson's Lilnar and Horary Tables. 

 In the Nautical Almanac for 1825, the example employed in 

 illustration of the excellent method of computation, published in 

 the Appendix to the Requisite Tables, stands thus corrected : 



3) 's Hor. Par. 

 G's App. Alt. 

 3) 's App, Alt 



t)ifiF. of App. Alt, 32 37 11 

 App. Distance 59 25 34 



59 27 

 69 11 52 — 6 30] 

 26 34 41 + 51 16 J 



N. vers. 



N. vers. 



51 46 Correction of Difference. 



1S7733 

 191351 



9.996819 

 . . 16 



Diff. ofTrueAlt. 31 46 25 

 True Distance 58 43 37 



Difference 3 33618 



Nat. n, 331172 



N. vers. 149712 



N. vers. 460884 



Table IX. 



Table X. 



Res. Lo§'. 9.996803 



Logar.^ 5.523250 



Logar. 5.52U053 



By Mr. Thomson's Tables, the result is obtained much more 

 expeditiously. Thus : 



5 's Hor. Par. 

 O'sApp. Alt. 

 App. Distance 

 First Corr. 

 Second Corr. 



59 25 31 



4 41 



5 15 43 

 Third Corr. T. XVI Il. 1 40 

 8um less 10° 



59 27 Tab. Log. 0.0211 0.0211 



59 12 . . . 0.5260 D's App. Alt. '26° 35' 0.809^ 



L. S. 0.9350 . L. T. . . . 1.2286 



. . 1.4821 Sec. Corr, L. 2.0589 



58 43 38, the true distance, v/ithin 1". 



The following comparative results will sufficiently show that 

 Mr. Thomson's tables agree in getieral with the direct methods of 

 computation as nearly as can be desired. 



True Uistancc. 



O / // 



43 31 1 



103 3 18 



51 9 50 



96 52 3 



63 53 17 



45 1 47 



Mr. Thomson, 

 o / // 



43 31 5 

 103 3 19 

 51 9 53 

 96 52 3 

 63 53 18 

 45 1 46 



