42 TRANSIT or VENUS, 1874. HONOLULU. 



I called Mr. Clapp to look at it. The planet was then about one third on. 

 Neither of us saw her entire disk, but we only spent a moment or two 

 looking at it, for just then the driving clock, which was being driven with a 

 light weight, stopped, and two or three minutes perhaps passe*d before things 

 were right again. Having replaced the micrometer, when the planet was 

 rather more than half on, I made the following three sets of measures of her 

 diameter in the direction parallel to the Sun's limb, on either side of the zero, 

 having carefully adjusted the focus : 



MICROMETER READINGS for DIAMETER of VENUS parallel to SUN'S LIMB. 



jst Set. 2nd Set. 3rd Set. 



r r r 



2-875 16-870 2-900 



2-846 i6'g2o Much " boiling." 



2-916 16-918 2-886 



3-145 (bad) 17-004 2-860 



2-810 16-922 2-820 



16-955 2-836 



The brasswork surrounding the reflecting prism had now become too much 

 heated to be touched by the hand. The micrometer-screw, however, was at 

 a considerable distance from the prism, and I do not suppose the value of one 

 revolution could be sensibly affected. 



As seen in the field of view of the double-image micrometer there was no 

 trace of the illumination in the planet's atmosphere seen at this time by 

 so many observers using Huyghenian eye-pieces. Had I seen it I should 

 probably not have known how to measure the distance between the cusps. 



When I judged that about five minutes remained before internal contact 

 I began to measure the cusps, Mr. Clapp counting aloud the seconds from 

 the clock. 



MEASURES of CUSPS before INTERNAL CONTACT. 



Micrometer Micrometer 



Clock Time. Reading. Clock Time. Reading. 



h m s r h m s r 



20.41. o 4'336 20.44.11 6-002 



20.41.30 4*690 20.44.23 6-270 



20.41.52 4-890 20.44.36 6-436 



20.42. 8 4-915 20.44.47 6-645 



20.43.31 5-700 20.45. I 6-918 

 20.43.44 5-804 20.45.25 7-466 



20. 43. 53 5-86o 20. 45. 43 7-755 



20. 44. 1 5-g85 



