214 TRANSIT OF VEXUS, 1874. KAILUA. 



The eye-end of tlie telescope was furnished with a fixed system of nine 

 vertical wires of spider's web and the usual pair of horizontal wires. There 

 was no micrometer. 



The Equatorial intervals of ilie, wires were found from, the whole of the 

 observed transits as follows, the signs being those proper for Equatorial stars 



when the illuminating lamp was "West : 



i n /n 



Wire a + 5.47-81 Wire/ i. 28-18 



b + 4.24-07 (j 2.55-55 



c + 2.53-34 h 4.24-89 



d + 1.27-41 k 5.52-68 

 e o. o oo 



The intervals of the wires a, c, e, g, and Je depend partly upon 200 transits 

 of clock stars and partly upon transits of close circumpolar stars ; those of 

 the remaining wires upon the circumpolar stars only. 



The Level Error was determined by means of a large striding level, the 

 bubble of which was graduated to single seconds by the makers. The 

 accuracy of the graduation was tested by Messrs. Troughton and Simms 

 before the instrument left England. 



The correction to the level error on account of inequality of the pivots was 



found to be 



// 



On 1874, October i3, i -oo with lamp West. 

 November 19, '99 



On this latter day the correction was determined in three positions of the 

 telescope, corresponding to 0, 30, and 60, Zenith Distance, and found to be 

 0" 97, 0" 99, and 1" 02 respectively. The pivots were therefore sensibly 

 circular. 



It was found that the Level Error was disturbed by the heat conducted 

 and radiated from the illuminating lamp. On December 3, Professor Forbes 

 found that when the lamp was east it lowered the east pivot 5" of arc. He 

 generally removed the lamp before applying the striding level. The syste- 

 matic discordance between the results for clock error obtained with the 

 reversed positions of the instrument (see page 217) is probably due to this 

 cause. 



The Level was adjusted November 26 and December 22. 



Table I. contains the determinations of the level error while the instrument 

 was mounted at Kailua. 



