68 



ASTRONOMICAL PHENOMENA AND PROGEESS. 



found by Mr. Burnham to be sextuple. The 

 double star No. 263 of South and Herschel's 

 Catalogue has five very minute stars in the im- 

 mediate vicinity of the two' bright components. 

 The system consists, therefore, of seven known 

 members. 



The Extended Nebulae of Sir John HerscheVs 

 General Catalogue. In a paper read by Cleve- 

 land Abbe, Esq., before the Philosophical So- 

 ciety of Washington, June 4, 1874, the author, 

 after referring to his previous researches on the 

 distribution of the nebula in space, proceeds to 

 inquire whether any definite relation exists be- 

 tween the planes of rotation of the elongated 

 or extremely elliptical nebulous masses. He 

 states the problem as follows : 



We have thus far studied the distribution in space 

 of the centres of the nebulae are there not planes 

 that have a definite relation to these bodies ? Among 

 the stars we have the Milky- Way and the orbits of 

 binary stars ; among the planets we have their or- 

 bits and equators, and the orbits of their satellites ; 

 among the nebulae we may expect to find analogous 

 planes, whose relations to each other and to those 

 already known cannot but be highly instructive. As 

 yet, we have but very few double nebulae, nor can 

 we for along time hope to determine the planes of 

 the orbits of any binary nebulae, if such exist ; on 

 the other hand, in regard to the axes of rotation of 

 nebulae or the planes of their equators, there is more 

 room for study; It is a plausible hypothesis, that 

 some nebulae are in rotation about their respective 

 axes, and only in the case of an irregular nebula do 

 we find presumptive evidence of numerous centres 

 of aggregation and rotation ; this latter class will 

 not now further claim our attention. Those nebulae 

 whose whole mass is rotating about a single axis 

 must appear to us either circular or elliptical, accord- 

 ing to our position in relation to that axis ; we might 

 then at once assume that every well-defined circular 

 nebula has its. axis of rotation directed toward us, 

 and might thus determine the position of the plane 

 of its equator ; this, however, would be hazardous, 

 since not only do we thus assume the fact of a rota- 

 tion, but also assume that the average rotation of all 

 nebulae is so rapid that, when viewed from any other 

 direction, they would present a sensibly elliptical 

 outline; moreover, often globular clusters of stars 

 are recorded as circular or globular nebulae. I have, 

 therefore, for the present, passed by the circular and 

 the ordinary elliptical nebulee, and have confined 

 myself to those described in Herschel's Catalogue as 

 exceedingly or very much extended. In regard to 

 them it may be remarked that, if these nebulae are 

 gaseous and without rotation, we can only explain 

 their apparent shape by supposing them to -be en- 

 dowed with a motion of translation to be, in fact, 

 wisps, like comets' tails ; if, on the other hand, they 

 be in a state of rotation, they must be fiat rings or 

 disks, or extended flattened ellipsoids, and we are 

 authorized to consider that the planes of their equa- 

 tors do sensibly pass through the position of the ob- 

 server; similarly, if the nebulous appearance be due 

 to the presence of lenticular or ring-shaped clouds 

 of asteroids, or of meteoric dust, we shall be able to 

 make a determination of the plane of the orbits of 

 these bodies. 



Having computed the right ascensions and declina- 

 tions of the south-poles of the fifty-nine nebulae in 

 question, I have also plotted them upon equal surface 

 charts similar to those used by Messrs. Proctor and 

 Waters, on which also have been drawn the limits of 

 the Milky-Way as given by those same gentlemen, ac- 

 cording to Heis and Herscnel. Owing to the fact that 

 the unresolved nebulae are, as a rule, far more numer- 

 ous near the poles of the Milky- Way than elsewhere, 



it follows at once that the greater number of the neb 

 ulae now under consideration are near these poles 

 and therefore our poles of rotation, if we may pro 

 sume to use that term, lie near the Milky-Way itself 

 but a careful enumeration shows us that in the North 

 ern Hemisphere these poles lie to the southward oi 

 tl*e central portion of the Milky Way, while in thi 

 Southern Hemisphere the reverse hold's good ; in fact 

 there exists a medial plane about which the poles oj 

 these nebulae cluster, and which is itself inclined t< 

 the plane of the Milky- Way at an angle of about 30 

 so that if the north-pole of the Milky- Way be ir 

 right ascension 12 h - 45 m - and declination 30, th< 

 pole of the plane near which the rotation axes of th< 

 nebulae lie will have about the same right ascension 

 but a declination of about 60. Numerically ex- 

 pressed, this latter plane is so situated that of fifty- 

 nine nebulae twenty-nine have their axes inclined t( 

 it by less than 10, and forty-two have their axes in- 

 clined less than 20. 



It is, I conceive, quite desirable that we should 

 on the one hand, have more accurate determinations 

 of the position-angles of these extended and ray- 

 like nebulae, and that, on the other hand, the reveV 

 sion spectroscope of Zollner should be applied tc 

 determine whether or not they be really in a stat< 

 of rotation. 



Mr. Abbe concludes : 



It may then in general be stated that, so far as w< 

 are able to determine the position of planes of rota- 

 tion among the nebulae, they do not show any such 

 tendency to agree with, each other as is shown ir 

 the orbits and equators of the major planets of the 

 solar system ; that, on the contrary, they are inclined 

 at all possible angles to each other, but have this 

 remarkable feature, that their mutual nodes clustei 

 about a point in right ascension 12 h - 45 m -, and north 

 inclination 60. 



Results of Spectroscopic Observations. 1. 

 Dr. Huggins's observations of different nebulaa 

 have shown conclusively that these bodies are 

 not moving with the same velocity as some of 

 the fixed stars. 2. The observations of Mr. 

 Lockyer have added zinc and aluminium to the 

 list of known solar metals. 3. The researches 

 of Secchi and Rutherfurd have shown that 

 there are three classes of stars : the spectra of 

 the first giving only hydrogen lines very thick, 

 and metallic lines exceedingly thin. This class 

 includes Sirius. The spectra of the second 

 class (which includes our sun) differ only in 

 degree from those of the first ; having medium 

 brightness and many lines. The third class is 

 distinguished by banded spectra, indicating the 

 existence of compounds. 



The Gold Medal of the Royal Astronomical 

 Society. At the annual meeting of the Royal 

 Astronomical Society on the 13th of February, 

 1874, their gold medal was awarded by the 

 Council to Prof. Simon Newcomb, of the Wash- 

 ington Observatory, for his researches on 

 the orbits of Neptune and Uranus, and other 

 contributions to mathematical astronomy. The 

 president, Prof. Cayley, in his address before 

 the Society explaining the grounds of the 

 Council's decision, reviewed in brief the prin- 

 cipal works of Prof. Newcomb, particularly 

 those on the orbits of the two outer planets. 

 He concludes as follows : 



In what precedes I have endeavored to give you 

 an account of Prof. Newcpmb's writings : they ex- 

 hibit all of them a combination, on the one hand, 



