August 25, 1910] 



NATURE 



249 



The magnitudes given for the whole object range from 

 90 to no, and show no marked increase or decrease with 

 the date. While some observers report a stellar nucleus, 

 others say that there is no definite nucleus, but there is 

 a central condensation in the nebulosity forming the head. 

 A short tail is reported by the majority of observers, M. 

 Guillaumc, using the equatorial couii of the Lyons 

 Observatory, with a power of 360, giving the length on 

 August II as about 1-5', and the direction as towards E. 



From observations made on .August 11, 13, and 15, Dr. 

 Kobold has calculated parabolic elements and an ephemeris, 

 the former giving the time of perihelion as .August 30-018 

 (Berlin M.T.). The Liter part of the ephemeris is given 

 below : — 



Ephemeris for 12/1. (.l/.T. Berlin). 



Mag. 



Owing to the short arc yet observed, the elements are, 

 of course, somewhat uncertain. From this ephemeris we 

 see that the comet is now moving very slowly in a direc- 

 tion slightly N. of W. through the constellation Serpens. 



PHOTOGR.iPHS OF D.iNiEi.'s CoMF.T, 1907^. — The advan- 

 tages to be secured from widespread cooperation, especially 

 in the study of the physical features of comets, are well 

 illustrated in a paper by Prof. Barnard which appears in 

 No. 194, vol. xlix., of the Proceedings of the American 

 Philosophical Society. There Prof. Barnard publishes 

 twenty-five plate reproductions of photographs secured by 

 him, with the 3-4 and lo-inch Bruce portrait lenses, 

 during the period July 11 to September 8. 



The physical changes depicted from day to day are very 

 remarkable ; but Prof. Barnard shows, by comparing his 

 plates with series taken at Lick and Juvisy, that much 

 shorter periods produced such great changes that some of 

 the features became recognisable with difficulty. The time 

 difference in the case of the Lick photographs is, generally, 

 about two hours, for the Juvisy plates about six hours, 

 yet even in the comparison between Yerkes and Lick there 

 are very distinct changes shown. In several cases it is 

 shown that a detached portion of the tail, although receding 

 from the head, was still moving sunwards in the path 

 followed by the comet. 



Precession and the Solar Motion. — In No. 614 of the 

 AstronomicAl Journal Prof. Boss publishes the results of 

 an investigation of the proper motions of more than 5000 

 stars, uniformly distributed over the whole sky, and 

 deduces therefrom the position of the solar apex and 

 corrections to Newcomb's values for precessions and for 

 the equinox of 1874. For the position of the apex he 

 derives, for 1875-0, R.A. =270-52° + 1-08° to +i-S3°, 

 dec- = +34-28° + 0-90° to +1-28°. Other solutions, for 

 selections of stars, such as those of different magnitudes 

 or large proper motions, are obtained, but they show no 

 sensible modifications of these values. 



For the velocity of the sun in space Prof. Boss finds 

 24 km. per second as a useful constant to adopt for the 

 present, and is of the opinion that the value (19-9 km.) 

 determined from spectroscopic observations is open to 

 objections inherent to that method. 



Further, he finds that his results strongly support the 

 hypothesis of the random motions of the stars, an hypo- 

 thesis which is directly opposed to the several ideas of 

 definite " star drifts " which have been published in recent 

 years. 



Calcium Vapour in the Sun. — No. i, vol. xxxii., of the 

 Astrophysical Journal contains a paper, by Mr. C. E. St. 

 John, which is full of important results concerning the 

 distribution and the circulation of calcium vapour in the 

 solar atmosphere. The research was undertaken in order 

 to provide data for the better interpretation of spectro- 

 heliograms in so far as they reveal the disposition and 

 inter-relation of the various solar layers. In 1872 Young 

 observed the reversal of the H and K lines in disturbed 



regions, in 1883 Lockyer photographed them, and in 1892: 

 Hale and Deslandres noted the reversals distributed over 

 the entire disc. 



With the splendid apparatus available at Mount Wilson,, 

 Mr. St. John has measured the various parts of the K 

 line (K,, K,, and Kj), and, referring these measures tO' 

 Fabry and Buisson standards, has determined the apparent 

 displacement at various points on the disc, thus deriving-, 

 data which indicate the conditions, altitudes, &c., under 

 which the emitting vapours exist. 



.Among other results, he finds that the vapours producing 

 the K, (absorption) line show a descending motion of 

 I -14 km. per sec, while the vapours producing the K, 

 (bright) line have, generally, an ascending motion of 

 1-97 km. per sec. A comparison of the angular velocities 

 obtained points to the vapour-producing K3 being at a 

 greater elevation than the hydrogen which produces the 

 Ha line. A comparison of the wave-lengths of K„ and" 

 K3 at, and away from, the limb indicates that these inter- 

 mediate and higher levels of the sun's calcium atmosphere 

 are not greatly disturbed by currents parallel to the solar 

 surface. 



From measurements of the widths of K, and H,, and 

 reasoning from their behaviour in the calcium arc spec- 

 trum, it appears that the quantity of calcium vapour in 

 the upper levels must be extremely small, while, from 

 similar considerations of the K, and H„ lines, the emitting 

 vapours would be relatively thick and dense. In approxi- 

 mate figures, the 5000 km. depth of the solar envelopes 

 above the photosphere is divided into 1500 km. for the 

 upper (absorbing) atmosphere and 3000 km. for the 

 emitting layer, leaving 700 km. for the layer which emits 

 the bright chromospheric radiations. A curious result is 

 that the K line persists for some 500 or 600 km. above 

 the level at which the H line ceases to show. 



On determining the wave-lengths of H, and K,, a differ- 

 ence of 34-810 A. was found, which differs by 0010 A. 

 from the value derived from Rowland's tables; this dis- 

 crepancy is probably caused by an error of that amount 

 in Rowland's wave-length for H. 



Mr. St. John's paper takes up forty-seven pages of the 

 journal, and there are other important results which are 

 too numerous for full discussion in these columns. 



OBSERVATIONS OF THE MOTION OF THE 

 UPPER AIR.' 

 HE two publications before us evidence the progress 

 whieh is being made in different ways in our know- 

 ledge of the upper currents of the atmosphere. Dr. Figee, 

 invalided home owing to the trying climate of Java, has 

 taken the opportunity of discussing the observations (286) 

 of the height of clouds, made at Batavia, 7° S., 107° E., in 

 1896-7, and later observations of cloud-velocity. The 

 results for height agree generally with the values obtained 

 in the same period at Manila, 14° N., 121° E. The 

 following table gives the heights in km., the mean values 

 for Paris and Potsdam being added for comparison : — 

 Cloud Ci. Ci.S. Ci.Cu. A.Cu. Cu. 



Batavia II'S ... I0'6 ... 6-3 ... 5-4 ... 174 



Manila 10-9 ... 11-4 ... 6-6 ... 53 ... 17 



Paris and Potsdam... 87 ... 76 ... 57 ... 33 ... I'S 

 The motion of the higher clouds shows different features 

 at the two places. In both the seasons, November-.April,. 

 May-October, the drift is towards the south-west at 

 Batavia, a result corroborated by the recent work of Van 

 Bemmelen, while at Manila it is towards the south-west 

 in the latter season, but nearly north in the former. The 

 value of the results in Dr. Figee 's paper can be rightly 

 appreciated only when they come to be utilised in pre- 

 paring an atlas of monthly charts showing the main 

 features of the circulation at the cirrus-level, an atlas 

 which is much needed at present. 

 The second paper is a discussion of fifty-one pilot-balloon 



1 (i) Royal Masnetical and Meteorological Observatory at Batavia : 

 Report on Cloud-Observations at Batavia made during the Internationat 

 Cloud-year 1896-1897 and subsequent years. By Dr. S. Figee. Appendix 

 ii. to vol. XXX. of the " Observations." Pp. 32. (Utrecht : Kemink and 

 Sons, loio.) 



(2) " Velocit!* e Direzione delle Correnti .Aeree alle diverse Altltudini 

 Determinate a Mez20 dei Palloni-Sonde e Piloli." By Dr. G. Pericle. 

 Pp. 55—126 ; 5 plates. (Milana : U. Hoepli, 1910.) 



T 



NO. 2130, VOL. 84] 



