306 COSMOS. 



The constructor of the powerful optical apparatus at 

 Parsonstown, who always discriminates between the result of 

 actual observation and the promises of a knowledge to which 

 we hope to attain, expresses himself with much caution 

 regarding the nebula in Orion, in a letter to Professor 

 Nichol of Glasgow, 37 dated Parsonstown, 19th March, 1846: 

 " In accordance with my promise of communicating to 

 you the result of our examination of Orion, I think I may 

 safely say, that there can be little, if any, doubt of the resolv- 

 ability of the nebula. Since you left us, there was not a 

 single night when, in absence of the moon, the air was fine 

 enough to admit of our using more than half the magnifying 

 power the speculum bears ; still we could plainly see that 

 all about the trapezium is a mass of stars, the rest of the 

 nebulse also abounding with stars, and exhibiting the charac- 

 teristics of resolvability strongly marked." At a subsequent 

 period (1848) Lord Rosse had not announced that his expec- 

 tations had as yet been fulfilled, although he cherished the 

 hope of being able to resolve the remaining portion of the 

 nebula into stars. 



to be similarly composed. A not unnatural or unfair induc- 

 tion would, therefore, seem to be, that those which resist such 

 resolution do so only in consequence of the smallness and 

 closeness of the stars of which they consist ; that, in short, 

 they are only optically and not physically nebulous. Although 

 nebulae do exist which, even in this powerful telescope (of 

 Lord Rosse) appear as nebulae, without any sign of reso- 

 lution, it may very reasonably be doubted whether there be 

 really any essential physical distinction between nebulae and 

 clusters of stars." 



87 Dr. Nichol, Professor of Astronomy at Glasgow, pub- 

 lished the letter above referred to in his Thoughts of some 

 Important Points relating to the System of the World, 18 iG, 

 p. 55. 



