238 TRANSIT OF VENUS, 1874. WAIMEA. 



founded on a bed of hard red clay, six feet below the surface of the ground. 

 It was protected by a small hut, which was almost entirely removed during 

 observation. 



The reticule consisted of five fixed wires of cobweb and one movable by a 

 micrometer screw, besides the usual pair of horizontal wires to define the 

 middle of the field. The value of a revolution of the micrometer screw was 

 found from a great number of observations of Polaris to be 65" '52. The 

 revolutions of the screw were numbered in the observing books with 

 increasing readings towards the head. "When the movable wire coincided 

 with the center wire, the reading was 



r 



10-043 on December 6, 

 10*045 on December i5, 

 10*046 on December 20. 



The reading 10 r< 043 has been used throughout the reductions. 

 The Equatorial intervals of the wires were found by means of the movable 

 wire and the known value of the micrometer screw as follows : 



// 



a + 399-94 

 b + 203-67 



C O'OO 



d 201 '08 

 e 3g6'2o 



When the micrometer head was on the east side of the telescope, equatorial 

 stars transited the wires in the order above. 



The Level Error (Table I.) was found by means of a striding spirit-level. 

 The original glass bubble of the level was accidentally broken at Honolulu, 

 and it was replaced by a spare bubble intended for the Altazimuth. The 

 value of the divisions was determined by attaching the glass bubble to the 

 telescope of the Altazimuth. 



1874. October 20, 21-26 divisions were found equivalent to 70" -3o; i div - = 3"'3i 



ii -io 37"'4o; 3"-3 7 



October 21, 18-45 62"'oo; 3"-36 



16-70 58"'43; 3"- 49 



16-00 55"'47; 3"'48 



24-26 77"- 18; 3"' 1 8 



November 6, 19-80 66"'77; 3"-32 



