•244 



NATURE 



[April ^2, 1920 



Our Astronomical Column. 



OccuLTATiON OF A SxAR BY Saturn.— Bad Weather 

 prevailed generally in Europe on March 14, when 

 Saturn occulted the star Leipzig I 4091, mag. 7-6. A 

 few observations were, however, secured, some of 

 them being published in Astr. Nach., 5042. Prof. 

 . Plassmann » observed the disappearance at. Miinster, 

 noting that at yh. 30m. G.M.T. the star was still 

 separated from the limb, at yh. 5-im. it was in con- 

 tact with it, while at yh. S-gm. the star had dis- 

 appeared. 



Messrs. K. Novak and V. Rolcik, observing at 

 Smichow, long. oh. 57m. 38s. E.Gr.,lat. 50° 4' 42" N., 

 noted the reappearance at 8h. 39m. 40s. G.M.T. 



Dr. Bernewitz, at Berlin-Babelsberg Observatory, 

 first saw the star at 8h. 39m. 34s. G.M.T. He noted 

 that at 8h. 39m. 51s. it appeared of full brightness, 

 and at 8h. 40m. 5s. the centre of its disc was dis- 

 tinctly separated from the limb. He states that the 

 marked red colour of the star made it easy to dis- 

 tinguish its light from that of the planet. He made 

 the only observation so far to h&nd of the appulse of 

 Titan' to the star,^ which occurred some four hours 

 after emersion from the planet. He states that Titan 

 did not occult it, but passed i" or ?." to the north of it. 



The extreme accuracy of Mr. Burnet's prediction is 

 noteworthy. He gave 7h. 5m. for the disappearance, 

 and 8h. 40m. for the reappearance. Owing to the 

 slowness of Saturn's motion, he thought it likely that 

 these times would be in error by several minutes. 



The Einstein Displacement of Spectral Lines. — 

 The Observatory for April contains communications on 

 this subject by Messrs. J. Evershed and C. E. St. 

 John. The former gives reasons for thinking that the 

 pressure in the photosphere is extremely low, so that 

 pressure may be eliminated as a disturbing factor. 

 Using forty-two iron lines, selected as not subject to 

 pole effect, he obtains a shift equivalent to a recession 

 of 0643 km. /sec. at the sun's centre and i-ooo at the 

 limb. But observations of Venus at various elonga- 

 tions support the idea that this is not an Einstein 

 effect, but a shift of all regions of the sun away from 

 the earth. It is remarked that it is difficult to accept 

 this as a physical reality, but no other explanation 

 has yet been found. He notes that some of the 

 carbon lines give an effect similar to the iron ones, 

 but somewhat smaller. The effect seems to varv for 

 different substances, and even for different lines of the 

 same substance, so that some modifying influence is 

 at work. 



Mr. St. John recapitulates his well-known investiga- 

 tion, in which he used certain lines of the cyanogen 

 band ; he then describes his recent work on mag- 

 nesium and iron lines. He finds from their weie-hted 

 mean a displacement of the same sign as the Einstein 

 prediction, but of only one-third or one-fourth of its 

 amount. Mr. St. John notes, however, that the dis- 

 placement varies with the intensity of the lines, beinj^ 

 greatest for lines either of verv great or very small 

 intensity. As the majority of the lines measured are 

 of medium intensity, the weighted mean is reduced. 

 He also notes that no lines have been used which 

 seemed unsuitable for the purpose, owing either to 

 their proximity to others or to their instability in the 

 arc spectrum. 



Stellar Spectroscopy at the Detroit Observa- 

 tory. — Vol. ii. of the Publications of this observatory, 

 belonging to the University of Michigan^ has lately 

 been distributed, and contains a preat number of 

 interesting studies of stellar spectra. Two may be 

 instanced in particular : the studv of variable stars 

 of Class Md, by Mr. Paul 'W. 'Merrill, traces the 

 changes of spectra that accompany the change of 



NO. 2634, VOL. 105] 



light, and discusses various suggestions of the cause 

 of variability. The one favoured by the author, is 

 somewhat analogous to the "geyser" theory, but, 

 instead of imagining a solid or viscous crust imprison- 

 ing the gases within, he substitutes a smoke-veil com- 

 posed of condensing gases (calcium is especially sug- 

 gested) in the upper regions of the stellar atmosphere. 

 This would act as a screen confining the heat of the 

 photosphere, until the accumulation of heat sufficed 

 to vaporise the screen. When the solid-crust theory 

 was propounded these stars were thought to be near 

 the end of their careers as suns, but from the small- 

 ness of their proper motions it now appears that they 

 are mostly giants. 



The other paper, by Mr. Laurence Hadley, deals 

 with the elements of ^' Ursae Majoris, the first 

 spectroscopic binary discovered. The orbit is fully 

 discussed from several series of observations. The 

 period is 20-53644 days, the eccentricity is 0518, and 

 the masses of the components x sin' t are respectively 

 1-83 and 179 in terms of the sun. It is noted that 

 Prof. Joel Stebbins finds no evidence of light 

 variation. 



Meteorologfy at Hong-Kong. 



A/r ONTHLY Meteorological Bulletins for the Royal 

 ■^'-|- Observatory at Hong-Kong for a considerable 

 period to August, 19 19, have recently been received. 

 They contain detailed results of observations made at 

 the observatory and the daily weather reports from 

 various stations in the Far East, prepared under the 

 direction of Mr. T. F. Claxton. For Hong-Kong 

 hourly values are given of barometric pressure, tem- 

 perature of the air and evaporation, direction and 

 velocity of wind, amount of rainfall, and duration of 

 sunshine. All the hourly observations are measured 

 from the self-registering records. Three-hourly ob- 

 servations are made of the character and direction of 

 motion of the clouds. Dailv values are also given of 

 the several meteorological elements. The normals used 

 for comparison with the means are for the years 1884 

 to 1918, a period of thirty-five years. From 1916 the 

 daily and mean hourly values of the principal meteoro- 

 logical records have been published in both C.G.S. and 

 British units, and with the January Bulletins tables 

 are given for the conversion of the several elements to 

 the respective units. Information is also supplied for 

 the reduction and correction of the instrumental ob- 

 servations. The December Bulletins give tracks of 

 typhoons and depressions in the Far East for the 

 year, and the divergence in the several months is well 

 shown. With the Daily Weather Reports, which contain 

 observations from forty-live stations in the Far East, 

 notices are given of the warning to coast ports, which 

 commonly state the position of typhoons when such 

 are in progress, and forecasts are given daily for the 

 twenty-four hours ending at noon. 



The annual report for 1917 contains a eornparison 

 of the Beckley anemograph with the Dines instrument, 

 extending over eight years ; the differences are remark- 

 ably consistent until the summer of 1917, when for 

 some unexplained reason, although noticed, the differ- 

 ences vary. A Richard dry- and wet-bulb thermo- 

 graph has been set up to replace the Kew photographic 

 thermograph. In section ix. reference is made to 

 sympiesometer observations, and hourly observations 

 are said to have been made for upwards of a year to 

 test the popular belief in the sympiesometer as a 

 weather forecaster. The remarks scarcely seem to 

 refer to a sympiesometer, which was essentially a 

 sailor's barometer in the first half of the nineteenth 

 century. It seems rather that the instrument tested 



