October 27, 192 1] 



NATURE 



291 



which connection the control and administration of 

 the Post Office is discussed. An important recent step 

 has been the development of local branches or groups 

 in the chief provincial cities, which will doubtless be 

 of value in extending the Guild's sphere of usefulness. 

 The main part of an address, entitled "The Message 

 of Science," delivered by Sir Richard Gregory before 

 the British Association, is reproduced as likely to be 

 of service to organisers of provincial groups. 



Messrs Wheldon and Wesley, Ltd., 38, Great 

 Queen Street, W.C.2, have just issued a most useful 

 botanical catalogue (New Series, No. 2), containing 

 particulars of upwards of 3000 second-hand works 



offered for sale by them. The catalogue is very con- 

 veniently classified under the following headings, 

 making reference easy : Early gardening, early 

 herbals, modern gardening, cacti and succulents, 

 flower garden and ferner\-, roses, fruit and vegetable 

 garden, grape vine and wine, greenhouse and hot- 

 house, landscape gardening and planting, orchids, 

 plant breeding, etc., early agriculture and husbandry, 

 modern British agriculture, grasses, forage plants, and 

 weeds, livestock, tropical and foreign agriculture and 

 gardening, food plants, beverages, etc., forestry- and 

 timber, industrial plants, medical botany, and 

 addenda. 



Our Astronomical Column. 



The Total Solar Eclipse of September, 1922. — 

 Prof. Campbell announces in Popular Astronomy for 

 October that it is proposed to send an expedition from 

 the Lick Observator\- to Wollal, in West Australia, to 

 observe this eclipse. The difficulties of landing are 

 considerable, but not insuperable, and the prospects of 

 good weather are better there than at any other station. 

 The principal item on the programme is the Einstein 

 problem. In order to shorten the necessary stay at 

 Wollal it is intended to take comparison plates of 

 the eclipse field at Tahiti on the voyage out, its lati- 

 tude being nearly the same as that of Wollal. .An- 

 other star field, culminating at night, will be photo- 

 graphed at both stations, to strengthen the basis of 

 comparison. 



Rlbidil.m in the Sln. — Dr. ^L N. Saha predicted 

 that the lines of rubidium might be detected in sun- 

 spot spectra, though invisible in the ordinary' solar 

 spectrum owing to considerable ionisation, which is 

 less in the sunspot, where the temperature is lower. 

 Prof. H. N. Russell has examined some fine spot 

 spectra photographed with the 150-ft. tower telescope 

 at Mount Wilson. He finds the two principal rubidium 

 lines at 780029 and 794764 distinctly visible, the 

 agreement in position being exact, and the relative 

 strength being also in accord. He therefore considers 

 the presence of rubidium established, and notes that the 

 lines of sodium and potassium are also strengthened 

 in the spot sf>ectrum, from a similar reason. 



Comets. — Mr. Innes and Mr. Wood obtained 

 numerous observations both of Encke's and Pons- 

 Winnecke's comets at the Johannesburg Observatorv 

 during July and August. Those of Encke are printed 

 in Astr. Xach, No. 5123. Even by August 8, onlv 

 twenty-six days after perihelion, the comet had be- 

 come extremely faint, and it was looked for in vain 

 on August 22 and 23. It has frequently been ob- 

 served that this comet is more difficult to observe 

 after perihelion than before it. The sun's heat appears 

 to produce a rapid expansion of the coma, rendering 

 it ill-defined. 



Dr. W. Baade, of Bergedorf Observatorv, obtained 

 a photographic observation of Reid's comet on 

 October id. ish. 3m. 54s. G.M.T., its position referred 



j to the equinox of 192 10 being R.A. 8h. 27m. 39-38s., 

 N. decl. 30° 11' 19-5''; the magnitude was 14, and the 

 indicated correction to Mr. Ebell's ephemeris was 

 — 19s., -32'. .This observation, made six and a half 



i months after discovery, will be of use in correcting 



I the orbit elements. 



I NO. 2713, VOL. 108] 



Finding of the Minor Planet Alinda. — The 

 search for this very interesting planet was referred to 

 in Nature for October 20. Astr. Nach. Circ, No. 32, 

 states that the planet has been found at the Konigs- 

 tuhl Observatory. The following obser\'ations were 

 made (referred to equinox of 1921-0) : — G.M.T. 

 October lod. i4h. i-2m., R.A. 3h. om. 7-15S., S. decl. 

 6° 35' 581', mag. 140; G.M.T. October i2d. 

 i4h. 33-4111., R.A. 3h. om. 32-965., S. decl. 7° o' 520'', 

 mag. 13-8. Stracke's value of the mean daily motion 

 requires the correction of +0-74", which is satisfac- 

 torily small. The planet is likely to be followed for 

 several months, as its linear motion in perihelion is 

 nearly the same as that of the earth. During some 

 revolutions of this planet the Jupiter perturbations will 

 be large, and it will be of interest to investigate the 

 alterjttion of the perihelion distance, which has the 

 value I- 182, ver}- little greater than that of Eros. 



Observ.^tions of Variable Stars. — Mr. W. J. 

 Luyten has published, as a thesis for his doctor's 

 degree, the results of observations of variable stars 

 made by him at Deventer and Leyden during the 

 years 19 15-19. His equipment gradually increased 

 from a field-glass and a 3-in. telescope to the 6-in. 

 equatorial at Leyden. His vision is unusually acute, 

 and he could observe stars down to magnitude 13-7 

 with the 3-in. and to 14-8 with the 6-in. The stars 

 observed include all t\pes of variables ; in the case 

 of Algol stars nothing was attempted beyond the time 

 of minimum, the light-curve being derived with much 

 greater accuracy from the use of the photo-electric 

 cell ; but light-curves were found for the Cepheids, 

 the note being made that minor fluctuations in the 

 curves are found in the case of S Sagittae only. New 

 periods and formulae are given for many of the long- 

 period variables. ^ Geminorum is found to conform 

 exactlv with a sine-cur\e, the mean magnitude being 

 3-938 and the amplitude 0165. In the case of 

 SU Cygni, Luizet's period is shortened by 0-00015 id. 

 to 3-845472d. It is noted that there is a great dis- 

 cordance in the interval from maximum to minimum 

 found by different obsers^ers. 



Several stars are then discussed for which Prof. 

 Turner and others had suggested sudden changes of 

 period or of phase. Mr. Luyten 's conclusions are more 

 in favour of slow progressive change of period than 

 of sudden jumps. He states that the observations 

 and discussions will subsequently be published at 

 greater length in Annalen van de Sterrewacht te 

 Leiden. 



