418 TRANSIT OF VENUS, 1874. KERGUELEN ISLAND. 

 The longitude of the transit pier is obtained as follows : 



Observer. J I. Number of Obs. 3> II. Number of Obs. Mean. Final Weight. 



s a h m a 



Coke 37 4 25 3 30-97 3 4.39.34-1 I 



Corbet 46-06 2 23- 11 2 4.39.34-6 i 



Perry 32-76 3 24-8 I 4.39.28-8 | 



Sidgreaves . . o 28-5 i ... 



Goodridge . . o 34 '65 2 ... 



Smith 25 "i i o 



Mean 4. 3g. 33 2 



It will be remarked that three of the observers have observed only one 

 limb of the Moon. The case of Corbet shows how unsafe it would be to 

 give any weight to observations of one limb only. Hence the final longitude 

 by this method is made to depend upon three observers only. 



(2.) Longitude of Observatory Bay from the observed Azimuths of the Moon. 



These observations must be divided into two classes those when a star 

 has been observed with the Moon, Class A., and those when no star was 

 observed, Class B. When the extreme instability of the transit instrument 

 in collimation and azimuth is considered, but little weight can be given to 

 the observations of Class B. The longitude by Altazimuth therefore depends 

 entirely upon Mr. Sidgreaves, for he alone observed both limbs of the 

 Moon. 



Thus we have, Class A., observer W S 



h m s 



By J) I., 1 8 sets of observations, longitude .... 4. 3g. 35' 26 

 By 5 II., 10 4.39.32-54 



Mean 4. 3g. 33 9 East of Greenwich. 



(3.) Longitude of Observatory Bay from the observed Occultation of 9 Tauri 

 by the Moon, 1874, December 20. 



The observation was made by W S with the 6-inch Equatorial. 

 The star disappeared at the Moon's dark limb, at 5 h . ll m . O s> 5 by the 

 Equatorial-clock. 



