226 



KNOWLEDGE. 



[OCTOBEK, 1902. 



components, of respectively foui-th and sixth inagnitiuli's, 

 are 4"-2 apart, and display— or, at least, displayed to early 

 observers* — eoulrasted tints of yellowish and purple. The 

 jmre radiance, nevertheless, of a Golconda dianiou<l would 

 match better their jointi spectrum. It is of a hit,'lily 

 primitive pattern; the lines crossinp; it are few and diffuse; 

 and they claim, .all but exclusively, a metalloidal origin. 

 Thoseof helium, toi^ether with the Hutfj^insaud Pickering 

 series of hydrogen, are unmistakiible,t and absorption by 

 oxygen and nitrogen will assuredly be found when carefully 

 looked for. 



One apparent anomaly remains to be mentioned. A 5'5 

 magnitude star in Scutum Sobieski (B.D. 10° 4313) came 

 out on one of Barnard's plates in 1892, surrounded by an 

 extensive tenuous halo.+ Yet in tlie Draper Catalogue, 

 where it is enrolled as No. 8198, a spectrum of the Capellan 

 variety is assigned to it. A.ssigned, indeed, with some 

 hesitation ; still we cannot but note the confirmatory 

 circumstance that the star is fainter chemically than 

 optically, while in helium-stars an opposite disparity is 

 always observed. A single good spectrograph would settle 

 the point. Nor should the genuine nebulosity of the 

 object be admitted on the unsupported evidence of an 

 isolated negative. Verification should be sought by 

 repeated and varied exposures, for the question whether a 

 solar star can be nebulously involved is really fundamental 

 to theories of relative stellar ages. 



It might have been anticipated that nebulous stars 

 would be found to shine pi-edominantly by emission — that 

 bright lines would be conspicuous in their spectra. Facts, 

 however, do not bear out this forecast. An immense 

 majority of bright-line stars are entii-ely free from 

 nebulous entanglements. The conditions are combined, 

 and that imperfectly, only in the stars of the Orion 

 trapezium, which give feelile signs of spectral emission ; 

 and in two members of the Pleiades group, Alcyone and 

 Pleione, neither of which is in such immediate connection 

 with nebulous structures as some of their dark-line asso- 

 ciates. Nor is there at present any reason to suppose that 

 the nuclear stars which, in planetary and annular nebulae, 

 appear the very foci of constructive activity, emit gaseous 

 radiations. Those that do — and they are very few — are 

 palpably not stars, but condensed wisps of cosmic haze. 

 Experience does not then warrant the current surmise 

 that the first stage of stellar development is marked by a 

 bright line spectrum. The I'equirements for its produc- 

 tion would rather seem to be independent of age, and to 

 arise under special influences, or through exceptional 

 peculiarities of constitution, lint the topic, being one of 

 the most arduous in astrophysics, is emphatically one 

 upon which dogmatic pronouncements would be out of place. 



ASTRONOMY WITHOUT A TELESCOPE. 



By E. Walter Maundee, f.r.a.s. 



XVIII.— VAEIOUS SKY EFFECTS. 



Theee are certain phenomena which lie very near the 

 border line of asti'onomy and meteorology ; so near that it 

 is difficult to say which science has the stronger claim to 

 take note of them. Amongst these, perhaps, those which 

 have the best claim to be included in the department of 

 astronomy are the strange bright clouds which were 

 discovered by Ceraski, and which were afterwards made 

 the object of careful study by 0. Jesse. These Luminous 



* Webb, " Celestial Objects," Vol. II., p. 182, Espin's cd. 

 t A. C. Maury, "Harvard Annuls," Vol. XXVIII., p. 111. 

 t Astr. Naeh., No. .3111, 



Night Clouds were utt<'rly unlike any phenomenon which 

 had Ix-en previously recorded, and their discovery, like 

 that of the Gegenschein, was a striking evidence that not 

 even yet have thi' fields of work which lie close at hand 

 been all explored. There is still an ample harvest to \w 

 reaped in more than one direction by the man who can 

 niinforce an observant eye by thoughtful patience. 



These luminous clouds were not visible at every time of 

 the year, but only during the nights of summer ; their 

 period of visibility for Btn-lin, where Herr .Jesse observed 

 them, being from' May 23rd to August Uth; a period 

 corresponding nearly to the season of continual twilight 

 for that latitude. Their light was derived from the 

 sun, which during tliat season is never more than 1« 

 bt>low the northern horizon, and tlie rays of which they 

 were enabled to catch by their great height ab^ve the 

 surface of the earth ; for the comparison of photographs 

 taken of them from different stations showed that they 

 ranged from fifty to fifty-four miles in elevation, or ten 

 times the height attained by light cirrus clouds. 



In appearance these night-clouds were of a brilliant 

 silvery-whiteness, slightly tinted at times with blue if ne,ar 

 the zenith, or with a reddish-yellow tinge if near the 

 horizon. They wei-e woolly and striated in character, and 

 repaid examination with a field-glass of large aperture, 

 by means of which they might tie traced considerably 

 further than the naked eye could follow them. 



The discovery of an order of clouds at a height above 

 the earth so greatly exceeding anything which had ever 

 been observed, even of the lightest cirrus, was remarkable 

 enough. More remarkable still were their variations. 

 For they were not by any means a permanent jihenomenon, 

 and diminished in frequency of appearance from the time 

 of their first discovery. From 1S85 to 1889, they wei'e 

 seen before midnight ; hater they could only be detected 

 in the morning hours. Their movements were more 

 interesting still, and were such as might be caused — so it 

 has been suggested — if, though travelling with the earth, 

 they were but lightly subject to its attraction, and ex- 

 perienced some retardation as they travelled ^vith it. 



From any point of view the existence of these clouds 

 must be regarded as most remarkable. That clouds should 

 exist at all at a height greater than the highest stratum to 

 which we owe twilight, and that so existing they should 

 be an occasional and variable phenomenon are entirely 

 unexpected discoveries, and still reni.aiu unexplained. Can 

 it be that they are one of the by-products of the great 

 volcanic eruption of Krakatoa in 1883? If so, they may be 

 looked for after any great series of volcanic outbursts, such 

 as that which commenced with the destruction of St. 

 Pierre in Martinique in May, 1902, even though these 

 eruptions cannot compare in violence with that of Krakatoa. 



Three striking sky-effects followed that great eruption 

 of 1883. The first was comparatively restricted both as to 

 area and time, and took the form of a remark.able coloura- 

 tion of lioth sun and moon. At Batavia, in Ceylon, at 

 various places in India, the sun was seen to be blue or 

 green ; blue when at the zenith, changing through green 

 and yellow to total obscuration near the horizon. A much 

 more lasting effect was th.at which received the name of 

 " Bishop's King," having been first reported from Honolulu 

 by the Rev. S.'E. Bishop on September .5th, 1883. This 

 ring was a remarkable species of halo to be seen on I'very 

 fine day surrounding the sun frcun its rise to its setting, 

 and, even occasionally round the moon. Thus in the 

 Stonyhurst Observatory report for 1883, it is stated : 

 " During the day tht> sun is invariably stirrounded by an 

 intense silvery brightness slightly tinged with green, and 

 at a distance of about 20' from the sun this tint sometimes 

 changes gradually into a pink or pale violet, and fades 



