*2 LIGHT SCIENCE FOR LEISURE HOURS. 



O 



where the transit began several minutes late, and ended 

 several minutes early, we should have a transit lasting 

 for a shorter time than as seen from the earth's centre : 

 and then, comparing what was observed at such a 

 station with what was observed at Nertchinsk, we should 

 have Halley's method applied under effective and 

 favourable conditions. But the southern stations to 

 which England sends observing parties areKodriguez and 

 Christ Church (New Zealand) ; * and at the former station 

 the transit begins late and ends late, while at the latter it 

 begins early and ends early ; so that at neither is there 

 the combination of a late beginning and an early end- 

 ing, required for the effective application of Halley's 

 method. 



Now there is a station a station which this country 

 ought unquestionably to occupy where the transit 

 would be even more shortened than it is lengthened at 

 Nertchinsk. This station is an Antarctic island on 

 which Sir James Eoss landed a party in 1846, and to 

 which he gave the name of Possession Island. It lies 

 due south of the southernmost extremity of New Zea- 

 land, close by the rugged shore-line of Victoria Land, 

 and within 18 degrees of the south pole. At this 

 station the transit will begin 6 minutes late and end 

 11-J- minutes early, or be shortened altogether no less 

 than 17^ minutes. Adding to this the lengthening of 

 the transit by 15^ minutes at Nertchinsk, we obtain a 



1 There has been a change as to the station selected in New Zealand, 

 from Auckland to Christ Church. The change is in accordance with 

 my own suggestions, so far as the application of Delisle's method is 

 concerned. 



