xxu 



President's Address 



results, which are here compared with the Greenwich and 

 with earlier deductions : — 





Parallax. 



Distance. 



1. 



2. 

 3. 



4. 

 5. 

 6. 



Greenwich results from transit of Venus, 1874 



Mr. Stone's results from do. 



From re-discussion of transit of Venus observa- 

 tions in 1769 



From observations of Mars, 1862 



M. Cornu's observations of velocity of light ... 



Le Verrier's classical deductions from planetary- 

 perturbations 



8-764 

 8-884 



8-910 

 8-940 

 8-860 



8-880 



Miles. 

 93,400,000 

 92,138,000 



91,870,000 

 91,561,000 

 92,388,000 



92,180,000 



These figures will give an idea of how modern observations 

 approximate to the solar parallax, but they must not be 

 taken as absolutely conclusive, as the results of the 

 American and German expeditions, as well as those of the 

 photographic methods adopted by both British and American 

 parties, have yet to be taken into account. Moreover, the 

 recent opposition of Mars has furnished another excellent 

 opportunity of testing the question, and there can be little 

 doubt that most trustworthy results will be obtained from 

 the combination of the northern and southern observations 

 which were secured from August to November last year, 

 and towards which our Observatory, as already mentioned, 

 has contributed a very complete series of measures. The 

 discovery at Washington by Mr. Asaph Hall of two 

 satellites of a planet hitherto regarded as being companion- 

 less, like Venus and Mercury, marks a new era in astro- 

 nomical science, and adds another laurel to the many 

 ali-eady won in the same field by our American cousins. I 

 have already spoken of the fruitless search we made here, 

 and the probable cause of our failure, and I may now add 

 that this fact, in connection with the comparative ease with 

 which the satellites were seen with the 2 6 -in. refractor 

 at Washington, has led to" comparisons between large 



