ASTRONOMICAL PHENOMENA AND PROGRESS. 



The resolution some years since of certain 

 nebulae, by means of telescopes of high power, 

 into what appeared to be congeries of stars, 

 gave rise for a time to the anticipation that all 

 nebulas might in fact be so resolvable. Indeed, 

 the opinion came to be expressed by some that 

 nebula) were but immensely distant systems of 

 suns, to which our own stellar system, with its 

 supposed rim in the galaxy, was comparable. 

 Now, however, it appears that the conclusions 

 to which the telescope unaided was leading, are 

 to be corrected by the revelations of the spec- 

 troscope: the mathematics of the rays, that 

 were leading the scientific judgment astray, are 

 to be checked by the disclosures of (what we 

 may call) their chemistry. (See SPECTRUM OB- 

 SERVATIONS.) True, a resolution of some nebu- 

 lae, even into actual stars, would not have 

 proved all nebulas to possess the like constitu- 

 tion ; and so, now, the proof by. the spectro- 

 scope, in one or more instances of resolution, 

 that the apparent stars so obtained are not real 

 stars, does not at once establish the conclusion 

 that no nebula? whatever are in reality star- 

 clusters. 



Messrs. Huggins and Miller having recently 

 (1864) examined with ihe spectroscope the light 

 of several nebula), including one or more which 

 some astronomers regarded as having been 

 shown to be star-clusters, found that their light 

 did not give the continuous spectrum indicative 

 of an origin in incandescent solid or liquid mat- 

 ter, but a gas spectrum only, and in most cases 

 consisting of three bright lines or bands, the 

 principal part of the space of an ordinary spec- 

 trum being dark ; while, in some instances, the 

 third line could not be seen, and in one at least, 

 that of the " dumb-bell " nebula in Vulpecula, 

 only the brightest of the three lines agreeing 

 in position with the brightest line of nitrogen 

 was detected. It thus became desirable, as 

 a conclusive test, to analyze the light of some 

 nebula which was supposed to have been with 

 certainty resolved into stars. A highly suitable 

 instance offered itself in the great nebula of the 

 "sword-handle" of Orion, the brighter portions 

 of which, near the trapezium, were held, by 

 Lord Rosse, Prof. Bond, Herschel, and others, 

 to be distinctly separated under a powerful tel- 

 escope into stars. Analyzing, now, the light 

 from the brightest part of this nebula, near the 

 trapezium, Mr. Huggins found it to present only 

 the three bright lines before met with, indi- 

 cating a gaseous constitution of the supposed 

 clustering stars of this portion. On the other 

 hand, each of the four bright stars forming the 

 trapezium gave a continuous spectrum; while 

 none of these gave dark absorption lines in the 

 positions corresponding to the bright lines of 

 the nebular spectrum, and in three of the four 

 cases the spectrum was brighter at the position 

 of those lines than were the nebular lines by 

 themselves. Finally, by successive observations 

 of its different portions, it was found that the 

 whole of this great nebula, so far as it lies 

 within the power of an 8-inch achromatic, emits 



light identical in character, the light from one 

 part differing from that from another in in- 

 tensity only. 



The real constitution, then, of this nebula, 

 alike in its supposedly " resolved " and in its ir- 

 resolvable portions, must be the same. Hence, 

 again, the separation of part of a nebula into 

 what appear to be stars, does not of itself prove 

 that the bright points so obtained are true stars. 

 On the contrary, these star-like points must 

 now be regarded as being, at least in some 

 nebulas, themselves merely gaseous bodies 

 denser aggregations, if would appear, of the 

 gaseous matter of which such nebula are at 

 large composed; and the question has been 

 raised whether it may not be by the continual 

 motion of these denser masses that the appar- 

 ent permanence of the general form of nebula 

 is maintained. 



Admitting, now, the validity of the infer- 

 ences just indicated, it is no longer necessary to 

 suppose the nebulae in reference to which such 

 conclusions hold, to be situated at so enormous 

 distances from our system as had of late come 

 to be believed. Some of the nebulae may be 

 much nearer to us than has been imagined ; and 

 with this supposition the fact of changes in 

 form in some of them (above alluded to) is not 

 at variance, if indeed the latter does not lend to 

 the former direct confirmation. It now be- 

 comes desirable, accordingly, to examine as to 

 whether a proper motion may not be detected 

 in some of these bodies. 



In another point of view, if the nebulous ex- 

 pansions in the heavens be, in any cases, the 

 visible material of stellar systems, forming or to 

 be formed, their spectrum would in such cases 

 be expected to give a variety of lines and groups, 

 showing the existence of a variety of chemical 

 elements. The three bright lines obtained by 

 Mr. Huggins in analyzing the light of nebulae, 

 and which have been supposed to indicate 

 nitrogen, hydrogen, and a third substance at 

 present unknown, could by possibility be 

 characteristic of matter in its most primary 

 forms. At least, a progressive formation of 

 some sort is suggested by the presence in some 

 nebulas of more condensed portions, and even 

 of a nucleus ; and nebulas which give a contin- 

 uous spectrum, and yet show little indication 

 of resolvability, such as the great nebula in 

 Andromeda, may still be gaseous, and may by 

 loss of heat or by other forces have become 

 crowded with portions of matter in a more con- 

 densed and opaque condition. 



Astronomical WorTcz and Memoirs. In addi- 

 tion to those works and papers already men- 

 tioned in this article, and in others in this vol- 

 ume appertaining to astronomical subjects, may 

 here be named the following: A Treatise on 

 Astronomy, by Prof. Elias Loomis, of Yale Col- 

 lege, 338 pp., 8vo, 'New York, 1865; Astronom- 

 ical and Meteorological Observations made at 

 the U. S. Naval Observatory during the Year 

 1862, by Capt. J. M. Gilliss, U. S. N., Super- 

 intendent, TOO pp., 4to, Washington, 1863 ; 



