656 THE POPULAR SCIENCE MONTHLY. 



effects how far-reaching and grand the design!" How deeply they 

 impress ns with the wisdom, power, and glory of the Creator and Gov- 

 ernor of the universe ! 



"We now come to consider the physical reality of the fundamental 

 assumption of the Nebular Hypothesis. Have nebulous masses a real 

 existence in the universe ? Is the Star-dust the "World-stuff a 

 physical reality, or a mere figment of the brain of the theorist ? If the 

 actual existence of self-luminous nebulous matter the chaotic ele- 

 ments of future worlds and suns can be established the fundamen- 

 tal assumption of Laplace loses the character of a pure hypothesis : his 

 concej3tion becomes a physical theory, which, in proportion as it is 

 Aerified by phenomena, approaches the domain of fact a vera causa. 



It was shown that the highly-diffused and attenuated matter con- 

 stituting comets, as well as that constituting the zodiacal light while 

 affording some suggestive analogies to nebulous masses do not fur- 

 nish examples in all respects identical with the supposed nebula of 

 Laplace. We are, therefore, compelled to fall back on Sir William 

 Herschel's opinion, that there are numerous nebula? which really con- 

 sist not of "clusters of stars, but of a diffused, self-luminous, vapori- 

 forrn matter. Such bodies are, beyond all question, self-luminous, but 

 the question is, Are they clusters of stars or true nebula? ? In other 

 terms, are they optically or physically nebulous ? 



For a long time, this question was keenly discussed, and opinions 

 fluctuated in regard to the tenability of the fundamental assumption 

 of the nebular hypothesis. It is well known that, since 1846, the ten- 

 dency of telescopic observations, as revealed by the magnificent instru- 

 ments of Lord liosse, and corroborated by the splendid achromatic of 

 Harvard University, has been to break down Sir William Herschel's 

 distinction between stellar clusters and true nebuke. After the sword- 

 handle of Orion was broken into glittering fragments, shining- with 

 separate and distinct lustre, Sir John Herschel himself was disposed to 

 abandon the opinion of his illustrious father. 



But the development of a new and wonderful branch of physical 

 science Jias recently furnished the most satisfactory proofs of the re- 

 ality of such bodies. We allude to the application of Spectrum Anal- 

 ysis to the study of the celestial bodies. The well-matured specula- 

 tions of Sir William Herschel, and the mathematical theory of Laplace, 

 have been vindicated from the doubt under which they have been la- 

 boring, and the early nebulous condition of the cosmical matter has 

 been demonstrated. The accomplished Sir John Herschel has been 

 permitted to witness the complete verification of the previsions of his 

 illustrious father ; to see the link connecting the past with the present 

 in the cosmogony of the universe which seemed to have been almost 

 ruptured by the extension of telescopic vision restored and strength- 

 ened by this new branch of physical investigation. 



