1 86 



NATURE 



[February 9, k 



report on "Atomic Structure," by Prof. Bohr, is in 

 preparation. An appeal for funds for a Duddell 

 memorial medal resulted in a sum of about 650^ being 

 raised. The committee dealing with the memorial has 

 asked Mrs. Mary G. Gillick to undertake the 

 preparation of the medal, which it is hoped will be 

 ready during the early part of 1922. 



The following lecture arrangements have been made 

 by the Royal College of Physicians of London :— The 

 Milroy lectures on "The Influence of Industrial Em- 

 ployment on General Health," by Dr. Major Green- 

 wood, on March 9, 14, and 16; the Goulstonian lec- 

 tures on "The Interpretation of Symptoms in Disease 

 of the Central Nervous System," by Dr. A. Felling, 

 on March 21, 23, and 28; the Lumleian lectures on 

 "Diseases of the Thyroid Gland," by Dr. H. Mac- 

 kenzie, on March 30 and April 4 and 6. The lecture- 

 hour in each case will be 5 o'clock. 



In a paragraph in Nature of February 2, p. 151, 

 it was suggested that the list of British research 

 chemicals issued by the Association of British Chemical 



Manufacturers should be revised and issued as soon 

 as possible, Mr. W. J. U. Woolcock, general 

 manager of the association, informs us that the sug- 

 gestion has been anticipated, and that a revised 

 and enlarged edition of this list is at the moment in 

 the press. Not only will this second edition contain 

 a larger number of organic chemicals, but inorganic 

 chemicals will also be included. 



Many libraries doubtless contain duplicates of astro- 

 nomical periodicals and books that are needed in other 

 institutions. For the purpose of facilitating their pur- 

 chase, exchange, or gift, the National Research 

 Council contemplates the compilation of a list of all 

 duplicates that can be spared. This list will be 

 mimeographed and widely distributed. Those who 

 have duplicates to dispose of are asked to send a list 

 of them to the National Research Council, Division 

 of Physical Sciences, 1701 Massachusetts Avenue, 

 Washington, D.C, U.S.A. A copy of the complete 

 Mst will be sent on application. 



Our Astronomical Column. 



Conjunction of Mars with a Star.— Mr. W. F. 

 Denning writes : — The planet Mars will make a very 

 near approach to the star /? Scorpii (third magnitude) 

 on the night of February 22. Mars will rise at 

 1.35 a.m. on the morning of February 23, and the 

 planet may be observed if the sky is clear from that 

 time until sunrise, with the star lying slightly to the 

 nr^'-th-west. It will be interesting to watch the 

 gradual approach of the two objects from the present 

 time up to the date of conjunction, and tjien to 

 follow them as the distance between them becomes 

 greater from night to night. On February 10 

 Mars will be 7° west of the star, and on 

 March 7 7° east, its motion carrying the planet daily 

 about half a degree eastward. The near approach 

 of the two objects may be followed with the unaided 

 eye, though the view will be much improved by means 

 of a field-glass or telescope. 



Comet Notes.— H. Mahnkopf gives the following 

 search ephemeris for comet I9i6'l (Taylor), due at 

 perihelion about 1922 June 13. It is for Greenwich 

 midnight. Magnitude about 15 : 



R.A. S. Ded. 



Feb. 10 I 26-1 4 21 Feb. 26 



14 I 32-8 3 18 



18 I 39-8 2 14 Mar. 2 



22 I 470 I 10 6 



R.A. S. Perl. 



h. m. ^ , 



1 54-5 o 5 



N. Dec). 



2 2-2 10 

 2 IO-2 2 6 



Log r, log A, February 2, 0-303, 0-357; February 18, 

 0284, 0-368; March 6, 0-264, 0-376. 



A new very faint comet, 1922a, was discovered by 

 Mr. W. Reid at the Cape on January 20 ; its place 

 on January 24d. gh. 34-3m. G.M.T. was R.A. 

 9h. 54m. 30-9S., S. decl. 33°- 46' 31"; daily motion 

 minus 56s., south 7'. 



Internal Motions in the Spiral Nebula M 81. — 

 The Astrophysical Journal for December contains Mr. 

 NO. 2728, VOL. 109] 



van Maanen's discussion of the internal motions in 

 this spiral deduced from two photographs taken with 

 the 60-in. reflector at Mount Wilson at an interval 

 of eleven years. The results of an earlier discussion 

 based on a six-year interval are in all cases con- 

 firmed in sign, but the numerical values are consider- 

 ably increased. Taking 000 1" as unit, the mean of 

 104 points measured gives the rotational component 

 as 38, the radial component outward as 13, the stream 

 motion (along the whorls of the spiral) as 39, and that 

 I transverse to the whorls as 7. The indicated periods 

 ! of rotation about the centre for four spirals are : — 

 For M loi, 85,000 years; for M 33, 160,000 years; 

 for M 51 (Canes Venatici), 45,000 years; and for 

 I M 81 (Ursa Major), 58,000 years. These figures are 

 all much smaller than any possible period of rotation 

 of the Galaxy, and seem to indicate an entirely dif- 

 ferent character for these objects. The only possible 

 way of avoiding this issue would seem to be the 

 adoption of Dr. Jeans's suggestion that the Galaxy 

 was originally much more compressed than it is now, 

 so that its period of rotation would have been shorter. 

 It is, however, emphasised, that the motion is not 

 pure rotation, but outward along the spiral arms. The 

 figures given have been corrected for foreshortening, 

 the plane of the nebula being inclined 49° to the 

 celestial sphere. The proper motion of the nebula 

 referred to fourteen faint comparison stars is +0014' 

 per annum in R.A. (great circle) and -0005" in dec. 

 Sixty-three stars in this region, of about the ninth 

 magnitude, have a mean motion of —0-0014" in R.A. 

 and —0-0047" in dec. (Greenwich Astrog. Cat., vol. 4). 

 It is therefore probable that the greater part of the 

 motion of the nebula in R.A. belongs to it, and not 

 to the stars. 



The author considers that the character of internal 

 motion established in several spiral nebulae supports 

 Dr. Jeans's theory that the spiral form is due to tidal 

 action arising from the approach of two nebulous 

 masses. 



