312 ANNUAL REPOKT SMITHSONIAN INSTITUTION, 1910. 



The years 1863 to 1890 were made fruitful by Huggins, especially 

 in the comparison of terrestrial and stellar spectra. He established 

 that the principal elements in the earth's surface strata exist also in 

 the atmosjriieres of the stars in the form of vapors and gases. Other 

 studies attempted to arrange the principal stars in the order of their 

 evolutionary history — in the order of their effective ages — from the 

 different appearances of the hydrogen and metallic lines in their 

 spectra. 



Huggins's observation of the spectrum of a nebula, for the first 

 time in 1864, has probably never been surpassed in dramatic interest 

 in any department of science. From the days of Sir William 

 Herschel it had been a much-discussed question whether the nebula? — 

 the faintly shining bodies which had not been resolved into separate 

 star images — were continuous in structure like a great gaseous cloud, 

 or were composed of stars unresolvable on account of their enormous 

 distances. To let Huggins speak : 



The nature of these mysterious bodies was still an unread riddle. Toward 

 the end of the last century the elder Herschel, from his observations at Slough, 

 came very near suggesting what is doubtless the true nature and, place in the 

 cosmos, of the nebulae. I will let him speak in his own words: 



"A shining fluid of a nature unknown to us. 



"What a field of novelty is here opened to our conceptions! * * * We 

 may now explain that very extensive nebulosity, expanded over more than 60° 

 of the heavens, about the constellation of Orion, a luminous matter accounting 

 much better for it than clustering stars al a distance. * * * 



" If this matter is self-luminous it seems more fit to produce a star by its 

 condensation than to depend on the star for its existence." 



This view of the nebulas as parts of a fiery mist out of which the heavens 

 had been slowly fashioned, began, a little before the middle of the present cen- 

 tury, at least in many minds, to give way before the revelations of the giant 

 telescopes which had come into use, and especially of the telescope, 6 feet in 

 diameter, constructed by the late Earl of Rosse at a cost of not less than 

 £12,000. 



Nebula after nebula yielded, being resolved apparently into innumerable stars, 

 as the optical power was increased; and so the opinion began to gain ground 

 that all nebula? may be capable of resolution into stars. According to this view, 

 nebula? would have to be regarded, not as early stages of an evolutional progress, 

 but rather as stellar galaxies already formed, external to our system — cosmical 

 " sandheaps " — too remote to be separated into their component stars. Lord 

 Rosse himself was careful to point out that it would be unsafe from his obser- 

 vations to conclude that all nebulosity is but the glare of stars too remote to be 

 resolved by our instruments. In 1S5S Herbert Spencer showed clearly that, 

 notwithstanding the Parsonstown revelations, the evidence from the observation 

 of nebula? up to that time was really in favor of their being early stages of an 

 evolutional progression. 



On the evening of August 29, 1864, I directed my telescope for the first time 

 to a planetary nebula in Draco. The reader may now be able to picture to 

 himself to some extent the feeling of excited suspense, mingled with a degree 

 of awe, with which, after a few minutes of hesitation, I put my eye to the 

 spectroscope. Was I not about to look into a secret place of creation? 



