194 



NATURE 



[Ma\ 



: 1 



the .M-tf-nce of nitrogen in the star can hardly be said to 

 1>. piovid. , ^ . 



Hiij^ht hands, possibly related to two found m gasfou* 

 1. l.uhi-, were s«-.n in the January spectra of the nova, 

 and a s|KCtrogram taken on March 30 shown that the nova 

 had then arrived at the nebula stage; bands at 01 

 AA 4«t.i, 495<», 5007. 5752 ±. and (>sbj were recorded. 



The Radial N'blocity of a Cyoni.— The study of th.rf v. 

 sprctrograms taken at the Pulkowa ObservaH>ry contirn.^ 

 Ih« variability of the radial velocity of a C'ygni. hrsl dl^- 

 covered at the Yerkes and Lick obsirvai()ru> in 1910. In 

 No. ^8 of the yUiUiUmgen der Nikolai-lhtuplstcrnu-arte zu 

 Pulkfl'U'o Herr «i. Neuimin publishes the data aiid results 

 h.' obtained from the measures, and directs spcial atten- 

 tion to the fact that the velocities deduced from eighteen 

 mttiillic lines varv considerably and consistently from those 

 obtained from the measures of the three hydrogen hues 

 H8, Hy, and HjS. Th.- range of velocities, relative to the 

 sun, as derived from the metallic lines, is from -176 to 

 + 2-47 km., and from the hydrogen lines -2 11 to 

 + 5.5 km.; the mean difference between the two sets of 

 velocities, from seven plates on which both sets were 

 measured, is +q-i± 1-2 1 km. per sec. .... 



Prof. Belopolsky confirmed this result by independent 

 reductions, using seven iron, two each calcium and 

 magnesium, one helium, and four hydrogen lines. Appar- 

 ently the helium line agrees with the hydrogen lines in 

 differing consistently from the lines of the various metals; 

 the results show a mean difference, metallic -hydrogen, of 

 + 7.1 ±0-9 km. On two of the spectrograms the calcium 

 lines H and K are apparently double. 



The Distribution of Variable Stars.— Plotting the 

 positions of 678 variable stars given in the Annuairc dti 

 Bureau des Longitudes (1909), M. Anestin, of Bucharest, 

 finds the known agglomeration in the Milky Way and the 

 condensations in Aquila, Lyra, Cygnus, Sagitta, Cepheus, 

 ..nd Cassiopeia. Near the N. pole of the galaxy, between 

 M,h. and I2h. R.A. and +20° to +40° declination, there 

 is hut one variable as compared with twenty in a fourth 

 th.- area in Aquila and Lyra. Long-period variables show 

 a t<ndencv to grouping, but the irregular variables are 

 more evenly distributed except for an agglomeration in 

 Cygnus. 



In the southern hemisphere, 664 variables crowd 

 towards the galaxv, but between 6h. and loh. R.A. there 

 appears a space almost devoid of them, which covers part 

 of the region, 6h. 30m. to i4h., also devoid of nova. The 

 region thus avoided bv the temporary and variable stars is. 

 . M Flammarion pointed out, the least complex and least 

 large area of the Milky \\ ay {L'Astrotwmie, April, 



The Variation of S Ar;e.— No. 3, vol. xxxiii., of The 

 Astrophysical Journal (April, p. 197) contains an interest- 

 ing paper by Dr. A. W. Roberts, in which the author 

 propounds a theory to account for the peculiar light-curves 

 of such " cluster-variables " as S Arje. The general 

 features of this type of light-curve are short period, a long 

 stationary' minimum, a very sudden rise to maximum, and 

 a Msurely decline to minimum. After carefully studying 

 the variation of S Arae, Dr. Roberts suggests that such a 

 light-curve may result from a combination of two distinct 

 variations. The primary curve would be that of a Cepheid 

 variable, depending upon an intrinsic variation of a bright 

 star. The superimposed curve would be that of an Algol 

 variable, and the theory demands that this shall be caused 

 by the eclipse of the' very bright, but relatively small, 

 satellite by a larger, dark primary ; the satellite is the 

 Cepheid variable. There are various objections to such a 

 theon-. but the main observed facts are in favour of it. 

 The great variation of the smaller star might be explained 

 bv the fact that the distance separating the pair is very 

 small ; thus the smaller companion may be revolving in a 

 path which carries it through the rarer atmosphere of the 

 larger star, the absorption of this atmosphere accounting 

 for the change in apparent brightness. 



The " Annuaire Astronomique " for iqiz. — The Royal 

 Obser\'atory of Belgium is to be congratulated upon getting 

 this useful Annuaire, for 1912. published so early, for 

 although it necessitates omissions from the revue section, it 

 facilitates the work of a number of the practical astro- 

 nomers the book is intended for. The comprehen^'v" "■;« 



NO. 2168, VOL. 86] 



of obw^rvatorie* i« omitted from IhU issue, but 

 publii^ihird every two <>r three years. In addition iw ll>c 

 uiiual tables, ephcmerides, " phenomena," Sec. 

 valuable article* on the tides, the universal : 

 and, in a lupplement bound with the A> 



♦h- 



////■. h'OYM. SOClEl \ ERSAZIONE. 



'PllK gentlemen '.•» conversazione vi the K 

 *■ was held in the society's rooms at Bur! 



on Wednesday, May 10. The ffl! ' 



received by Sir .'\rchibald Geikie, K 



soiiety, and many objects and exj 



interest were exhibited. During the evening the Ho«i. 

 R. J. Strutt gave a lecture on the afterglow of the electric 

 discharge and on an active nwdification of nitrogen, and 

 .Mr. Joseph Barcroft lectured on adaptation to high alti- 

 tudes in relation to mountain sickness. Experiments wt-i.- 

 shown by Prof. Strutt to prove that the well-known 

 " afterglow " of GeissW*r tubes containing air is a ph<»- 

 phorescent flame, produced by the reaction of nitric oxii!' 

 and ozone formed in the discharge. It was shown th.;: 

 nitrogen gives rise to a different kind of aftergk>w. 'I ■■ 

 latter is regarded as resulting from the formation of • 

 active modification of nitrogen, which slowly reverts to :: • 

 ordinary form with luminosity. It was also shown ih.^r 

 acetylene is spontaneously inflammable in this aclivt 

 nitrogen, and burns to cyanc^en, the flame showing the 

 characteristic spectrum of that gas. 



Following our usual custom, we give a summary of the 

 official description of exhibits, related subjects being here 

 brought t(^ether for convenience of reference. 



The Astronomer Royal. — (i) Model of orbit of Jupiter's 

 eighth satellite. The model shows the path of the satellite 

 around Jupiter from 1908 to 1916 as predicted by Dr. 

 P. H. Cowell from the observations made in IQ08 and 

 1909. The orbits of satellites VI. and VII. and of the 

 inner satellites are also exhibited to scale and in theii 

 proper planes. The scale is 80 inches equal 1 solar unit, 

 or I inch equals 1,160,000 miles. (2) Globe showing thf 

 motions of the two main star stream*. The model has 

 been constructed to show how an examination of the direc- 

 tions of motion of the stars reveals the presence of two 

 great streams of stars. The statistics of the motions in 

 different parts of the sky are summarised by the diagrams 

 on the globe ; it can be seen that for each region there are 

 two " favoured directions " of motion in which the stars 

 move in greatest numbers. These directions are traced on 

 the globe, and converge to two apices. The Director.^ 

 Khedivial Observatory. Hehvan, £/:y/)/.— Photographs of 

 Hallev's comet taken with the 30-inch Reynolds reflector 

 by Mr. H. Knox Shaw. The photographs exhibited cover 

 the period from April 16 to June 10, 19 10. Lowell 

 Observatory. .Arizona. ['..S..4.— (i) Photographic negatives 

 of Hallev's comet taken at the Lowell Observatory, May 4 

 to June' 5, 1910. (2) Plates of slit spectrograms of 

 Hallev's comet, (j,) Plates of slitless spectrograms of 

 Hallev's comet. Three important deductions follow from 

 the photographs and spectrograms :— {i) The identification, 

 bv Dr. Slipher. of the three chief bands in the comet s 

 spectrum as those which Mr. Fowler has shown to be the 

 bands of carbon monoxide when under very low pressure. 

 (ii) The totallv diverse gaseous constitution pointed out bv 

 Dr. Slipher between the emissive constituents of the head 

 and tail— the bright gases of the one being strong wher- 

 those of the other are weak, and vice versa, (iii) Measure- 

 ments by Prof. Ivowell on knots in the photograph showed 

 an accelerated vek>city away from the head, as follows : — 



Angular dis'anre from 



the nucleus to the point 



measured in the tail 



Velocity of the poiat 



of the uil away from 



the nucleus 



Knot I 

 Knot 2 

 Knot 3 

 Knot 4 



This, taken in connection with the spectrc^rams, disclosed 



