LONGITUDE. OBSERVATIONS OF INGRESS. 493 



giderably greater than the degree of accuracy with which the instrument is 

 capable of measuring azimuths, the true longitude can be inferred by a 

 simple proportion. Of all methods of obtaining the longitude by means of 

 the Moon's motion, that of observed azimuths is the most troublesome. [It 

 is, however, used successfully at Kerguelen and at Burnham, as far as the 

 number of observations permits. G. B. A.] 



[For the same reasons as in the similar stages of operations in Part III. 

 and Part IV., I have suppressed the details of the Altazimuth Reductions in 

 this Part. G. B. A.] 



Table VII. contains the mean result for longitudes of Burnham, inferred 

 from the observations of each day exhibited separately for the preceding and 

 following limbs of the Moon. 



ON THE LONGITUDE OF BURNHAM. 



The Meridional Transits of the Moon, Table VI., give IP. 29 m . 10 S '6. 

 The Observed Azimuths, Table VII., give IP. 29 m . 20 s -5. 

 The latter observations are less numerous, and probably inferior in quality. 

 If we give weights to the results in the proportion of 3 : 1, we shall obtain for 

 final longitude of Burnham 



IP. 29 m . 13 S -1 East. 



OBSERVATIONS OF THE INGRESS OF VENUS, 1874, DECEMBER 8 (GREENWICH 

 RECKONING), DECEMBER 9 (NEW ZEALAND RECKONING). 



After describing the preparations for observation, and the unfavorable 

 character of the weather preceding the Ingress, Major Palmer proceeds as 

 follows : 



Thelirst glimpse after first contact was obtained at 18 h . 41 m . 36 S> 25 sidereal ; 

 the planet was then seen to have advanced apparently about three-eighths of 

 her diameter on the Sun. Both Sun and planet could only be just made out 

 through the clouds, without any coloured shade to the eye-piece. Having 

 adjusted to center of field, I now exchanged the eye-piece for the double- 

 image micrometer, and between this and 18 h . 54 m . made a dozen attempts 

 to effect measures of diameters and cusps, in the few brief glimpses (never 

 exceeding 8 to 10 seconds) which were now and then afforded by partial rifts 

 in the dense masses of cloud. My efforts, however, were quite unavailing. 



