THE COMING TRANSIT OF VENUS. 33 



difference of duration of fully 33 minutes. Nothing 

 like this difference was available in the transit of 

 1769; nothing like it will be available in 1882. I 

 do not know the circumstances of the transits of 

 2004 and 2012, but it is altogether unlikely that the 

 opportunity of applying Halley's method will be so 

 favourable during either of these transits as in 1874. Be 

 that as it may, however, it is absolutely certain that 

 no opportunity equal to that which will be afforded 

 during the transit of 1874 will recur for one hundred 

 and thirty-two years, nor has such an opportunity been 

 ever before offered to astronomers. Absolutely the 

 best opportunity of applying Halley's ingenious method 

 which has ever been afforded, or will be afforded for 

 more than a century and a quarter, is available to astro- 

 nomers during the approaching transit. The duty of 

 seizing this opportunity belongs assuredly to our 

 country, which alone has colonial possessions close to 

 the station in question, and which alone also has sea- 

 men stilt living who have actually set their foot on 

 Possession Island. 



I must confess that when, four years ago, I indicated 

 this opportunity, I thought that it would have been 

 seized at once. I thought that reconnoitring expedi- 

 tions would quickly have been prepared, and that by 

 the present time complete arrangements would have 

 been made for landing an observing party on Posses- 

 sion Island in due season for the required observations. 

 It would have been a matter of complete indifference 

 to me whether this had been done with or without 



D 



