Iviii Proceedings of the South African Philosophical Society. 



93 millions of miles. Viewed from such different standpoints, one 

 would naturally imagine that the apparent position of a star would 

 be changed, or if the stars were at different distances from the 

 earth their relative positions would be changed. But previous tO' 

 Henderson's time no astronomer had been able to produce satis- 

 factory evidence of anything of the kind. The conclusion would be' 

 that the stars are infinitely distant, or rather so distant that the 

 orbit of our earth round the sun when viewed from the nearest star,, 

 with an instrument as powerful as the best telescopes we possess, is 

 but a speck in invisible minuteness. Here was a bar to any sound 

 conclusion as to the dimensions of the universe — a problem that had 

 defied the utmost skill of man to solve. How far beyond the power 

 of measurement were these distances ? Were they just beyond that 

 verge or infinitely beyond it ? Would any clue be given us as to 

 the dimensions of the immensities of systems beyond our own ?' 

 The conception of infinite distance is an impossibility— the mind 

 loses itself in fruitless attempts to realise what infinite distance 

 means, and yet here were those mysterious stars apparently proving 

 to the baffled philosopher and astronomer that their distances were 

 infinite. 



I wish that I could stop to explain in detail the method of 

 Henderson's observations and the grounds of his conclusions — the 

 subject of distances of fixed stars might well occupy an address for 

 itself. I can only state now that in the years 1835-40 the two 

 great masters of practical astronomy, Bessel in Germany and Struve 

 in Eussia, devoted themselves to the problem, and finally produced 

 evidence, each in case of different stars, of a really measurable 

 parallax. But whilst those great masters had been exhausting the 

 resources of their skill in observation, and that of the astronomical 

 workshops of Europe in supplying them with the most refined 

 instruments for this purpose, a quiet, earnest man had been at work 

 at the Cape, and, loithout hnoiuing it at the time, had really made^ 

 the first observations which gave decisive evidence of the measure- 

 able distance of a fixed star. Henderson deduced his remarkable 

 result after his return to England, but previous to the results of 

 Struve and Bessel. Probably Bessel' s result was the most con- 

 vincing, and it was to Bessel that in 1842 was awarded the gold 

 medal of the Eoyal Astronomical Society. Sir John Herschel, in 

 presenting the medal, said : " Should a different eye and a different 

 circle continue to give the same result, we must of course acquiesce 

 in the conclusion ; and the distinct and entire merit of the first dis- 

 covery of the parallax of a fixed star will rest indisputably with 

 Mr. Henderson. At present, however, we should not be justified in 



