186 SCENERY OF THE HEAVENS. 



those of the resolvable class. The latter, with more or less difficulty, were separated by 

 the telescope into stars ; the former gave no indication of being similarly constituted when 

 interrogated by the highest instrumental power. Hence arose the famous hypothesis, that 

 a chaotic kind of material exists, occupying extensive spaces, self-luminous and phosphor 

 escent, which presents an endless variety of contour and condensation, resembling in many 

 instances A sheet of fog, but exhibiting in others an aggregation into spherical or oblong 

 masses. This was conceived to furnish a key to the origin of the worlds and systems of 

 worlds disclosed around us to unveil, likewise, the primitive state and early history of 

 the solar universe diffused nebulosities having advanced gradually by the mutual 

 attraction of their particles into dense spheroids. 



The theory was premature, for improved telescopic power has largely disproved its data. 

 After looming mysteriously in the sky, the great nebula of Orion yielded to the giant 

 instrument of Lord Rosse, and disclosed its stellar construction. The history of the event 

 is thus given by Dr Nichol : "About Christmas 1845, I had the pleasure of visiting 

 Parsonstown, and saw the nebula, through that mighty tube. It was owing to the 

 incompleteness of the instrument and unfavourable weather the first time that the grand 

 telescope had been directed towards that mysterious object : and though Lord Rosse 

 warned me that the circumstances of the moment would not permit him to regard the 

 decision then given as final, I went in breathless interest to its inspection, Not yet the 

 veriest trace of a star ! Looming unintelligible ae ever, there the nebula lay ; but how 

 brilliant its brighter parts ! How much more broken the interior of its mass ! How 

 innumerable the streamers now attached to it on every side ! How strange, especially that 

 large horn to the north, rising in relief out of the dark skies, like a large cumulus cloud ! 

 It was still possible, then, that the nebula might be irresolvable by the loftiest efforts of 

 human art ; but doubt continued to remain. Why, in an inquiry like this, the concurrence 

 of every favourable condition is needful to success, may be readily comprehended. It is 

 its aim to discern, singly, a number of sparkling points small as the point of a needle, 

 and close almost as the particles of a handful of sand ; how easy, then, for any unsteadiness 

 in the air, or any imperfection in the instrument, so far to diffuse the light of each that 

 they would merge into each other, and thus become confounded in one mass !" Throughout 

 the winter, the noble owner and constructer of the instrument resolved to seize every 

 favourable opportunity to penetrate, if possible, the constitution of this wonderful object ; 

 and at length addressed the following note to Dr Nichol: "March 19, 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 as to the resolvability 

 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 nebula also abounding with stars and exhibiting the characteristics 

 of resolvability strongly marked. ROSSE." It has subsequently been shown more fully to 

 consist of an immense irregular assemblage of stars, which were not previously discernible 

 for want of sufficient optical aid. Hence it is morally certain, that all these irresolvable 

 objects are really star-systems, the -components of which are not distinguishable by reason 

 of their remoteness, though collectively they gleam across those spaces, the magnitude of 

 which is perfectly confounding. 



The different appearances presented by the same nebulae, when viewed by inferior and 

 more powerful telescopes, is very striking. The following are examples of the same object 

 as seen in Sir John Herschel's instruments and those of Lord Rosse. The Crab Nebula, 

 which the right-hand figure in the cut shows with the strange appendages brought to 

 light by the mirror of Lord Rosse, appeared to Sir John Herschel as a dull ellipse, like 



