April 21, 192 1] 



NATURE 



247 



tides to determine their bending in a magnetic field. 

 By this means he shows that these swift particles are 

 ordinary a-particles of mass 4, and not doubly charged 

 particles of mass 3, such as are produced by the 

 passage of o-particles through nitrogen and oxygen. 



Messrs. Pastorelli and Rapkin, of 46 Hatton 

 Garden, E.C.i, have issued a new list of their glass 

 and metal hydrometers and specific-gravity instru- 

 ments for use in chemical laboratories and for indus- 

 trial purposes. The list includes not only all the hydro- 

 meters generally used in laboratory and technological 

 determinations, those of Twaddell being particularly 

 well represented, but also an extensive variety of 

 salinometers and saccharometers. It is. interesting to 

 see that hydrometers have now a wide application in 

 industry, being no longer confined to brewing and 

 distilling, but required for petrol and other oils; by 

 electricians for accumulators; in the meat-pickling 

 trade; in laundries for testing starch; as "lacto- 

 meters " for milk; by tanners, who call them "barko- 

 meters "; while there is even a special hatter's hydro- 

 meter for shellac solutions. 



Mr. John- Murray is to publish for Lord Haldane 

 a work entitled "The Reign of Relativity," in which 

 the principle of relativity will be dealt with in its 



philosophical aspect, and not merely as interpreted in 

 mathematical physics. The departments of biology, 

 psychology, the State, and religion will be considered 

 in the investigation, and illustrations of the principle 

 of relativity in this wider application will be drawn 

 from literature, art, religion, and recent physical and 

 natural science. Another book in Mr. Murray's new 

 announcement list is "The Great Malaria Problem 

 and its Solution," by Sir Ronald Ross. The work 

 will be largely an autobiographical record of the incep- 

 tion, progress, and ultimate success of the campaign 

 against malaria. 



Mr. R. F. Granger, of Lenton Fields Climato- 

 logical Station, Nottingham, who made naked-eye 

 observations of the partial eclipse of the sun on 

 April 8, writes to say that he saw Venus clearly, 

 though he could see no stars. He noticed that faint 

 cloud formed at 8.15 and disappeared at 9.0; "it 

 probably lay in the damp layer at the top of the 

 turbulent region, and appeared to be formed by direct 

 cooling." Daisies closed, but chickens took no notice 

 of the darkness. 



Erratum. — Nature of April 14, p, 218, ist col., 

 line 6 from bottom : For F. C. Cruikshank read 

 F. G. Crookshank. 



Our Astronomical Column. 



Poxs-VVinnecke's Comet.— The following provi- 

 sional elements of Pons-Winnecke's comet have been 

 deduced with the aid of the recent observations. 



T 1921 June 13-950 G.M.T., w 177° 41' 37", node 

 93° 24' 19", incl. 19° u' 31", log a 0-51403, e 0-69138, 

 q 1-008. 



Ephemeris for Greenwich Midnight. 



^■A. Decl. Log r Log a 



h. m.' s. o ^ 



April 18 16 12 43 39 36 N. 0-1050 9-6378 



20 16 17 59 40 21 0-0996 9-6213 



22 16 23 32 41 6 00942 96043 



24 16 29 30 41 53 o 0889 9-5868 



26 16 35 52 42 42 0-0836 9-5696 



28 16 42 38 43 18 0-0783 9-5505 



30 16 50 6 44 o 0-0731 9-5313 



May 2 16 58 13 44 39 0-0680 9-5114 



4 17 6 49 45 19 0-0630 9-491 1 



6 17 16 26 45 54 0-0580 9-4699 



8 17 26 56 46 28 0-0532 9-4481 



10 17 38 32 46 56 0-0486 9-4253 



12 17 51 25 47 18 0-0440 9-4017 



The comet will be nearest the earth (distance 



12,500,000 miles) on June 6. The earth passes the 



node on June 25, about nine days after the comet. 



Reid's Comet. — ^This comet was on the verge of 

 naked-eye visibility more than a week ago. It should 

 be easily so visible when the moon is out of the way. 

 M. Ebell has computed new elements from which the 

 following ephemeris (for Greenwich midnight) is 

 taken. The elements differ only slightly from those 

 given in Nature for March 31. T is May 10-01 and 

 log 5 000403 : 



R.A. N. Decl. R.A. N. Decl. 



h. m. s. o , h. ID. s. o , 



April 22 204154 33 44 May 2 21 16 10 6824 

 24 20 45 20 40 16 4 21 38 8 74 53 



26 204936 47 II 6 222422 8037 



28 2Q 55 22 54 20 80 31 22 84 49 



30 21 332 6129 10 42737 8450 



NO. 2686, VOL. 107] 



Values of log r, log A: April 22, 00223, 98292; 

 .April 30, 0-0096, 9-8017; May 8, 00042, 9-8640. The 

 high north declination will facilitate observation. 



Mr. W. F. Denning writes : — " Reid's comet was 

 faintly visible to the naked eye on the morning of 

 April 16 at 3.20 G.M.T. The comet's perihelion will 

 occur on May 10 next, and when the moon leaves the 

 evening sky about April 24-25 the comet should be 

 easily visible. It will then be situated in Cygnus 

 and a few degrees south of oCygni. Its motion is 

 carrying it rapidly northwards, so that on May 2 the 

 comet will be found 2° or 3° south-west of /3Cephei. 

 It should be readily found with a field-glass, and will 

 probably be easily within reach of the unaided eye." 



Fixed Calcium Lines in Early Type Stars. — Sine* 

 the discovery in 1904 of the fact that the H and K 

 lines of calcium in the star 8 Orionis did not share 

 in the large displacements common to all the other 

 lines, a similar effect has been observed in manv other 

 stars. A considerable amount of literature has thus 

 accumulated on this subject of "fixed" calcium lines, 

 which has now been collected and discussed bv Mr. 

 R. K. Young in a very useful summary published in 

 the Journal of the Royal Astronomical Society of 

 Canada (vol. xiv., p. 389). It appears that nearly all 

 the stars having this peculiar characteristic are of 

 early B type, and this forms a strong argument 

 against the theory that the stationary calcium lines 

 have their origin in a cloud of vapour lying between 

 us and the star. It is also difficult to account for 

 their origin by assuming an extended nebulosity en- 

 veloping the star and not partaking in its motion, 

 sinca in a very close pair of stars observed by Plaskett 

 only one showed this effect; and in the Pleiades, 

 which are known to be surrounded bv such a nebula, 

 the effect is not seen at all. The author holds rhe 

 opinion that the calcium vapour giving rise to the 

 fixed lines forms part of the star's own atmosphere, 

 but is much more extended than the proper reversing 

 laver. 



