

July 27, 1893] 



NATURE 



\o\ 



Changes in the Spectrum of /3 Lyr.e.— At the Pulkova 



bservatory, the new spectroscope has been adapted to the 

 !arge refractor, and among many of the stellar photographs 

 already obtained several are of ;8 Lyrse, the changes in which 

 are described by Belopolsky in the June number of the Meniorie 

 della Societii iicgli Spettroscopisti Italiani. The measures of 

 position of the lines were made relatively to the solar lines by 

 superposing a solar spectrum on that of the star. A general 

 examination of the plates showed the following details, the most 

 remarkable lines being D.j, 501 •4UU, 492/ii/i, F, 47Im>', 448mm, 

 44 7w- Fconsistednearlyalwaysoftwobrilliant rays, one of which 

 would disappear or become very dim, and between these could oc- 

 casionally be seen a dark line ; in the vicinity of F occasionally 

 is seen also another dark line. The analysis of the changes in the 

 bright F line indicates that its duplicity depends on one or both 

 of the dark lines, or in other words, that we have here a case of 

 superposition of the bright and dark lines. The period is nearly 

 of 13 days' duration. At the principal minimum of the star, the 

 bright F becomes single, the dark lines being situated one on 

 the edge and the other alone. At the maximum, F becomes 

 double, but the component on the violet side is very thin. At 

 secondary minimum, F is double and symmetrical. Little change 

 takes place at the following maximum, the component on the 

 red side being a little thinner than the other; after this maxi- 

 mum it becomes a dark line. 



With regard to the dark F line, M. Belopolsky says that this 

 seems to consist of two, but it is seldom that they are separated ; 

 it is suggested that a second ray may mask the changes in 

 wave length of the other, thus accounting for the irregular 

 changes. 



The Helium line undergoes two changes; sometimes it 

 disappears altogether, while at other times it appears double. 

 Its period of duplicity is put down as 7 days. The group 

 448-447W is defined as very complicated, and presents the same 

 changes as the F lines, consisting of dark and bright lines and 

 changing their positions like the components of the F lines. 

 This paper is accompanied by a diagram showing the positions 

 of the star in the curve of brightness at the time of exposure, and 

 also by copies of several of the spectra. 



The Variable Star Y Cygni. — Among recent papers on 

 variable stars, that by Prof. N. C. Duneronthe elements of the 

 variable star Y Cygni is of great importance. [Kongl : 

 Vetenskaps Akademiens Fothandlinger, 1892, No. 7). This 

 star is of the Algol type, and its variation is limited nearly ex- 

 clusively to a small portion of its period during which it descends 

 in a few hours to a minimum, to regain in about the same time 

 its ordinary brightness. Since its discovery by Chandler in 

 1886, it has been very constantly observed, and it is perhaps on 

 this account that Prof. Duner can give such a complete story. 

 Considering the odd and even minima separately, he deduces a 

 formula which gives very small values for the residuals obtained 

 from the observed minus calculated times, and to put it shortly he 

 is led 10 the conclusion that the star Y Cygni consists of two 

 stars of equal magnitude and brightness, moving in an elliptic 

 orbit, the plane of which passes through the sun, and whose line 

 of apsides makes an angle with the line of sight. The time of 

 revolution is 2 days 23 hours, 54 minutes, 43 '26 seconds. Prof. 

 Duntr, at the latter end of this paper, gives the ephemeris and 

 tables of interpolation of the times of the odd and even epochs 

 in Paris mean time. 



New Determination of the Constant op Universal 

 Attraction. — A new and original method of determining the 

 mass and density of the earth was described in our issue of 

 July 13 (p. 251). 



The following further information on the same .subject is 

 interesling. The first experiments gave for the value of K — 

 the constant of gravitation — 



K = 6-8o X io-«. 



Determining the mass of the earth, by substituting this value of 

 K in the formula 



^ R- 



when M and R represent the mass and radius of the earth 

 respectively, and where 



g = 981 and R = 637 x 10' centimetres, 

 NO. 1239, VOL. 48] 



the value obtained was 



M = 585 ^ 10'^ grammes, 



whence the density of the earth was found to be 



D = S-4I. 



We here enumerate the different values that we possess with 

 regard to the earth density — 



Plumb-line at Schiehallien (Maskelyne and Playfair) 4713 



,, Arthur's Seat (James) S'3i6 



Pendulum at Mont Cenis (Carlini and Giulis) . . 4-94 



,, Harton Coal Pit (-\iry) 6'S6S 



Torsion-Balance (Cavendish, 1798) 5-48 



„ (Reich, 1838) 5-49 



(Baily, 1843) 5-66 



,, (Cornu and Bailie, 1872) . . . .5-5 -5"s6 



The Coronal Atmosphere of the Sun. — Prof. Janssen, 

 in Comptes Rendtts, No. 2, for July 10, communicates an inte- 

 resting note on the history of facts which have demonstrated 

 the existence of the coronal atmosphere of the sun. 



Variable Stars. — In the Astronomical /outnal, No. 299, 

 M. Paul Yendell publishes more observations of the maxima 

 and minima of variable stars. Among some of those referred 

 to are Y Ophiuchi, X Cygni, T VulpecelL-e, X, W, V, and U 

 Sagittarii. 



GEOGRAPHICAL NOTES. 

 The Times has received the following telegram from Dr. 

 Nansen, dated Berlevaag, July 21. Berlevaag is about sixty 

 miles west of Vardo, on the north coast of Norway :— " We are 

 leaving Vardo for Yugor Strait (between Waigatz Island, south 

 of Nova Zembla, and the coast of Russia), where thirty sledge 

 dogs will be waiting for us. We then proceed along the Siber- 

 ian coast eastward past Cape Chelyuskin to the Olenets river, 

 near the Lena, where another twenty-six dogs will be waiting 

 for us. We then turn northwards, and hope to reach the west 

 coast of the New Siberian Islands in the end of August if the 

 ice is not bad. The latest information about the ice condi- 

 tions in that quarter is favourable. We then proceed direct 

 northwards until we get fast in the ice. If we meet with new 

 land we shall follow along its west coast northwards. When 

 there is no more open water we shall allow the Fram to drift 

 with the ice. Everything has gone on well up to the present. 

 The Frai?i is a splendid strong ship and will stand the ice-pres- 

 sure well. She is deeply laden with coal, but that is a draw- 

 back which will soon be remedied. The accounts of the ice in 

 the White Sea and the Barents Sea are not favourable. There 

 has been much ice, but hope it has now improved ; the ice 

 changes quickly. I have good hopes ; if we only get through 

 the Kara Sea in good time I feel certain the prospects of success 

 are good. — Fridtjof Nansen." 



The July number of the Geographical yournal commences 

 the second volume. Amongst other papers of interest there is 

 one of some importance on South-west Africa by Count Pfeil, 

 who has taken a leading part in settling the interesting German 

 colony at Windhoek, east of Walfisch Bay. Regarding Port 

 Nolloth, he points out the curious fact that the great v\ aggon 

 traffic set up by the copper mines of Ookiep has led to the up- 

 rooting for fuel of all the little bushes which formed the sole 

 vegetation of the country. The light soil deprived of its pro- 

 tection has changed into drifting sand, and there is no prospect 

 of this artificial desert being redeemed by natural agencies. 



In the last number of the Scottish Geographical Ma«azine 

 there is an abstract of an important paper by Prof. H. Wagner 

 on the teaching of geography in Germany, which gives an ad- 

 mirable resume of the growth to university rank of that 

 study, the adequate recognition of which is confined to 

 Germany, and the true proportions of which have never yet 

 been realised in this country. 



In the Asiatic Quarterly Review Prof. Sayce shows that the 

 term Sinaitic peninsula applied to the region between the Gulfs 

 of Suez and Akaba is a misnomer ; all the evidence available 

 proving that Mount Sinai really stands somewhere in the ranges 

 of Mount Seir, the exact site being still unknown. 



