June 26, 1890] 



NATURE 



209 



Spectrum ends abruptly in the orange. The light of the 

 brighter part is not uniform ; probably it is crossed either by 

 bright lines or by lines of absorption" (Phil. Trans, 1866). As 

 yet we know nothing of the spectra of the components of 

 any star cluster except in the case of ihe loose cluster of 

 the Pleiades, and in that case we know that the .spectra are all 

 of the same type — namely, Group IV. It seems pretty evident 

 that the stars of the cluster in Hercules cannot have spectra 

 of this kind ; otherwise, their integrated light would not end 

 abruptly in the orange, and the irregularities would only be 

 obvious in the blue end, where the thick hydrogen lines ought 

 to be visible. The absence of red light would lead rather to 

 the supposition of bright lines than dark ones. Further in- 

 vestigations, with considerable optical power, may therefore 

 lead to interesting results. It may be noted that Vogel, in 

 1872, recorded simply a continuous spectrum, but his attention 

 had probably not been directed to Dr. Huggins's statement. 



(2) The question of the periodicity of the appearance of the 

 bright lines in /3 Lyra? cannot yet be said to have been satis- 

 factorily settled, and as the star will he visible for some months, 

 further continuous observations are desirable. It is not neces- 

 sary here to recapitulate all the observations which lead to the 

 conclusion that there is a periodicity in the spectrum. Gothard 

 has probably given more attention to the star than any other 

 observer, and he succeeded in following the variations of the 

 line D;) through several periods "from a bright, almost dazzling 

 light to complete disappearance. . . . The variation is most 

 marked in the case of D3 ; it is much less striking in the hydro- 

 gen lines, although they, and probably also the dark bands in 

 the red, are subject to a periodical variation." The period has 

 been provisionally estimated as 7 days, but it does not seem to 

 depend upon the fluctuations in the Irightness of the star. In 

 my own observations I have found that the bright lines in this 

 star are best seen when no cylindrical len-; is employed, and this 

 has also been noted by other observers. Further observations, 

 to be of any value, should be made as frequently as possible, 

 and over a long period. 



(3) Duner describes the spectrum of this star as one of the 

 most magnificent of Group IT., the bands 1-9 being wide and 

 dark. He also states ihat there is a narrow band between bands 

 3 and 4. As the spectrum is a bright one, this is a good oppor- 

 tunity for comparing the dark flutings with the brightest flutings 

 of manganese, lead, and magnesium. In the recently issued 

 volume of spectroscopic observations at Greenwich, Mr. Maunder 

 states that he has found the bright green band in o Herculis 

 coincident with the brightest carbon fluting and possessing the 

 same characteristics. A similar comparison should also be 

 made with a Scorpii, 



(4 and s) These stars, according to the observations of 

 Gothard and others, have spectra of the solar type and of Group 

 IV. respectively. The usual more detailed observations are 

 required in each case. 



(6) The spectrum of this variable has not yet been recorded. 

 The magnitude ranges from about 9 to < 13 in a period of 

 about 188 days. There will be a maximum about July 2. 



A. Fowler. 



Greenwich Spectroscopic Results. — These results for 

 1888 contain observations of 7 Cassiopeise, MiraCeti, o Orionis, 

 a Herculis, 6 Lyrap, R Cygni, P Cygni, /3 Pegasi, and Comets 

 a and e 1888. On October 5, 1888, ten measures were made of 

 a bright line in the violet part of the spectrum of Mira Ceti ; the 

 mean wave- length found was 434S'37. indicating that it was the 

 third line of hydrogen. F and Dg were searched for on this 

 occasion, but without success. The spectrum of o Herculis was 

 compared with those of carbon and manganese, as given by a 

 Bunsen flame on several occasions, and it is noted : "The green 

 band of the carbon spectrum accorded, both as to position and 

 appearance, with the bright interspace or ' zone ' to the blue of 

 Band VII. (Duner's numeration). So far as the dispersion em- 

 plojed would show, no accordance could be more complete, both 

 as 10 the position of the edge and the gradation of the fading," 

 The blue carbon band was also found to present an approxima- 

 tion in position and appearance to a bright zone in the blue. 

 1 he wave-length of ihe brightest bands in the manganese spec- 

 trum was determined as 5579, and that of the more refrangible 

 edge of Duner's Band IV. as 5592, whence it is concluded that 

 the connection of the spectrum of the star with the manganese 

 .s^.ectrum did not appear to be made out. A bright line at 

 5873 '92, that is, D3, was measured in /3 Lyrae on August 10, 

 1888, was seen less distinctly a month later, and was found 



NO. 1078, VOL. 42] 



again to be quite distinct on September 19 ; two days later, Ds 

 was seen very bright, and C and F were also visible. Dg was 

 visible, but faint, on October i ; F could not be seen, and C 

 was only suspected. On October 19, C and F were not visible 

 as bright lines, but were first suspected as dark lines, whilst D3 

 was glimpsed occasionally as a feeble bright line. R Cygni was 

 observed on September 21, D3 wrs identified with probability 

 in its spectrum, and F with certainty ; and, on October i, ten 

 measures were made of the F line in P Cygni. Comet a 1888 

 was observed on April 19, 1888 ; its spectrum appeared mainly 

 continuous ; two bright bands were just glimpsed, coincident 

 with the bands in the green and yellow of the spectrum of a 

 Bunsen flame, the band in the blue being suspected. On May 3 

 the spectrum was practically wholly continuous, traces of the 

 green band only being suspected. Comet e 1 838, observed on 

 November 27, showed a local ill-defined brightening, corre- 

 sponding nearly to the great carbon band, but apparently further 

 towards the blue, otherwise it was perfectly continuous. 



The Rotation of Venus.— Signor Schiaparelli has re- 

 cently made an extended inquiry into the question of the 

 rotation of the planet Venus, and has brought many facts to 

 light concerning it {Rendiconti del R. Istituto Lombardo, vol. 

 xxiii.). He finds, from observations of very definite spots, that 

 the time of rotation of the planet is 224 7 days — that is to say, 

 Venus, like the mnon, and probably Mercury, rotates on her 

 axis in the same time that she takes to make a sidereal revolu- 

 tion around the sun ; the axis of rotation being nearly per- 

 pendicular to the plane of the orbit. By investigating the 

 writings of previous astronomers who have estimated the rota- 

 tion period, Signor Schiaparelli concludes that those observa- 

 tions which have been supposed to fix the time as about 24 

 hours are open to question. Domenico Cassini's observations 

 of bright markings in 1866-67 are shown to have been wrongly 

 interpreted, a discussion of them indicating that they also support 

 a period of rotation of 2247 days. 



GEOGRAPHICAL NOTES. 



The Russian Geographical Society has received fresh news 

 from M. Grombchevsky as to his attempts to penetrate into 

 Tibet from the north. In the autumn of 1889 the expedi- 

 tion explored the Uprang, a tributary of the Raskem-daria, 

 tried to enter again into Kanjut, and, having failed to do so, 

 explored the tributaries of the Raskem river which flow from 

 the Himalayas. On November 21, M. Grombchevsky, accom- 

 panied by two men only, crossed the Kara-korum Pass, and 

 went to the Pahnu mountaineers, who live by sheep-breeding, 

 and suffer a good deal from the Kanjut robbers. On December 7 

 the expedition was at the small fort of Shahi-dulla-hodja ; the 

 winter had come, and the thermometer fell in the nights to 

 — 20° Celsius. Nevertheless, M. Grombchevsky, with two 

 men only and a guide, explored the passes leading to Kara- 

 korum across the Raskem ridge. The tent had to be 

 abandoned, although the temperature was - 35°, and the party 

 was soon obliged to return. On January 7, after having fol- 

 lowed for some distance the Karakash river, the small party- 

 began its ascent of the steep slopes of the Tibet border-ridge. 

 The plateau itself proved to be a desert, 17,000 feet high, upori 

 which a few yaks, Kulangs, and mountain sheep were grazing. 

 A very high ridge, called by M. Grombchevsky the Yurung- 

 kash ridge, was crossed, the pass receiving the name of 

 "Russian." But the horses of the expedition were quite at- 

 tenuated, and on January 13 the party was brought into a 

 perilous condition by a frightful snow-storm and a temperature 

 of - 27°, without having either a tent or any kind of fuel. 

 M. Grombchevsky was compelled to return, marching all day 

 long. After having made another unsuccessful attempt at 

 crossing the Hindu-tash Pass, the expedition went to Kilian. 

 and thence t<> Polu, thus connecting its surveys with those of 

 Prjevalsky. A telegram received from New Marghelan, in 

 Russian Turkestan, announces that the explorer and his men 

 have returned safely, and are making new schemes for further ex- 

 ploration. A map, annexed to the last issue of the Izvestia of 

 the Russian Geographical Society, embodies the surveys made 

 by M. Grombchevsky in 1888 and M. Grum-Grzimailo in 1887. 



In the course of last jear the Geographical Society of Berlin 

 published no fewer than thirty-nine remarkable maps. Three 

 of them are repioduced from those of Mercator, now in the 



