VENUS ON THE SUN'S FACE. 73 



so that they may accurately determine the latitude 

 of the temporary observatories they will erect. This 

 is a work requring skilled observers and recondite 

 processes of calculation. Hence it is that the cost of 

 sending out these observing parties is so considerable. 



The only English party which will apply Halley's 

 method of observation is the one which will be stationed 

 at Crozet Island or Kerguelen Land. This part of 

 their work will be comparatively easy, the method only 

 requiring that the duration of the transit should be 

 carefully timed. In fact, one of the great advantages 

 of Halley's method is the smallness of the expense it 

 involves. A party might land the day before the 

 transit and sail away the day after, with results at least 

 as trustworthy as those which a party applying Delisle's 

 method could obtain after several months of hard work. 

 It is to this, rather than any other cause, that the small 

 expense of the observations made in 1769 is to be 

 referred. And doubtless had it been decided by our 

 astronomical authorities to apply Halley's method 

 solely or principally, the expense of the transit-obser- 

 vations would have been materially lessened. There 

 would, however, have been a risk of failure through 

 the occurrence of bad weather at the critical stations ; 

 whereas now as other nations will doubtless avail 

 themselves of Halley's method the chance that the 

 transit-observations will fail through meteorological 

 'causes is very largely diminished. Science will owe 

 much to the generosity of England in this respect. 



It is, indeed, only recently that the possibility of 



