130 SIR JOHN FREDERICK WILLIAM HERSCHEL. 



to the constitution of the vast star system, and to the nature of the 

 nebulte, occurred, as he modified the principle of interpreting- his ob- 

 servations. In 1811 he writes : " I find that by arranging the nebuhie 

 in certain successive, regular order, they may be viewed in a new light, 

 which cannot be indifferent to an inquiring mind." He now expressed 

 the opinion that these aiebulai did not consist of multitudes of stars, 

 but of some self-luminous substance of exceeding tenuity. He recog- 

 nized the existence of this luminous vapor amidst large tracts of the 

 heavens, and regarded it as lying within the limits of the galaxy. Nay 

 more, he believed this vaporous matter to be the material from which 

 the stars were made. According to this view, vast as has been tlie age 

 of our galaxy, it has not completely formed itself into compact bodies. 

 For many years he had held that all the nebulae are composed of stars. 

 He now believed that some nebulce were not of a starry nature ; that a 

 luminous matter existed in the universe in an elemental state; that 

 the globular nebulae were the earliest formed and most advanced in 

 growth 5 and that this vaporous or luminous matter lay within the line 

 of the milky way, and formed part and parcel of its constitution. 



This new view taken by Sir William Herschel of the construction of 

 the heavens, whether as respects extension in space or duration in time, 

 is singularly impressive. It implies indeed an enormous diminution of 

 dimensions. It reduces the supposed countless millions of stars around 

 Orion to chaotic vapor. It contracts distances, so far beyond our star- 

 system as not to be separately discerned by the most powerful glass, 

 into spaces midway only between us and our galaxy. In reducing these 

 distances many hundred times, this theory reduced the vastness of the 

 objects many million times. But, on the other hand, it showed the 

 milky way to be a more wonderful scheme than had ever been sup- 

 posed. Vast as has been the period of its existence it had not yet 

 entirely shaped itself into stars; over the regions where it extends, 

 enormous masses of nebulous matter are still condensing into suns, and 

 it becomes to the imagination a stupendous laboratory where systems of 

 worlds have been produced and countless suns have had their genesis. 

 Despite the ingenuity of illustration and incontestable force of reason- 

 ing by which Sir William Herschel sought to establish this bold hyyoth- 

 esis, it has not won general favor since his day. Observation seems 

 conclusively to show that the greater the optical power of the telescope 

 the more certain is the evidence that the nebulae are aggregations of 

 stars. Sir John Herschel, too, with his usual reverential caution about 

 controverting his father's dicta, seems to entertain this last opinion. 

 " It may very reasonably be doubted," he wrote, '' whether there is any 

 essential physical distinction between clusters of stars and those nebulae 

 which my father regarded as composed of a shining nebulous fluid, and 

 whether such distinction as there is be anything else than one of degree, 

 arising merely from the excessive minuteness and multitude of the stars 

 of which the latter compared with the former consist." 



