24 TRANSIT OP VENUS, 1874. HONOLULU. 



(2.) Longitude of Honolulu Station from tlie observed Zenith Distances of the 

 Moons Upper and Lower Limbs. Tables IX. and XL 



63. Honolulu is very favourably situated for determining the longitude in 

 this manner in the winter months, as the observations can be secured when 

 the Moon's orbital motion is more or less perpendicular to the horizon, 

 a condition, it is hardly necessary to remark, which was always observed. 

 The observations were taken by Mr. Nichol and myself, fundamental 

 time being taken from the transit-clock. Six or eight vertical transits of 

 the Moon's limb, and two of a well-known star pretty near the Moon, con- 

 stituted a complete observation ; the instrument being, of course, used in 

 reversed positions. The observations of the Moon are, on the average, 

 rendered differential by means of those of the stars, and thus any error that 

 might creep in from the error of the transit-clock having been determined 

 by different persons is eliminated from the mean. 



64. The observations of the stars were first reduced in the following 

 manner : The observed clock-time of vertical transit of the mean wire was 

 reduced to local sidereal time by the application of the clock corrections in 

 Table VI. This was the sidereal time at the transit pier and not at the 

 altazimuth pier, as it should have been. With this slightly incorrect sidereal 

 time, and adopted co-latitude 68. 42'. 3"'l, was computed the star's tabular 

 zenith distance given in the seventeenth column of Table IX., using the 

 fundamental place of the star in Table VII. 



The correction due to the difference of time (O s> 074) between the transit 

 and altazimuth piers was then applied, and the true tabular zenith distance 

 obtained. This was compared with the observed zenith distance with the 

 following results, for the excess of the tabular quantity when the star is east, 

 the reverse when the star is west : 



EXCESS of the TABULAR ZENITH DISTANCES of STARS over the observed ZENITH 

 DISTANCES, with changed sign for STARS WEST of the MERIDIAN. 



Observer, Nichol. Observer, Tupman. 



// // 



1874, Oct. 5, a Leonis -f 4-3 1874, Oct. 3, 7 Leonis + 4-0 



19, Fomalhaut + 3'3 7, a Leonis r3 



24, Procyon ....... o'3 i5, <r Sagittal ii 3-o 



27, a Aurigae + ro 23, ,3 Andromedse. . . 1-2 



28, Procyon + 2'8 25, Tauri 0-8 



