422 



NA TURE 



[April i, 1922 



Our Astronomical Column. 



Ratios of Planetary Distances. — Mr. F. A. 

 Black, 57 Academy Street, Inverness, sends us a 

 communication in which he points out a fairly close 

 approximation which connects the ratios of the 

 planetary distances. Using the names of the planets 

 to denote their respective mean distances from the 

 sun, then 



Mercury + Earth J upiter + Uranus 

 Venus + Mars ~ Saturn + Neptune' 



The logarithms of the ratios are 9-79050 and 978935 

 respectively. The approximation is sufficiently close 

 to be interesting, though it is unlikely that it has any 

 j)hysical basis. It will, of course, be observed that 

 corresponding members of the inner and outer 

 planetary groups occupy corresponding places on 

 the two sides of the equation. 



Reid's Comet, 1922 (a).— Mr. H. E. Wood has com- 

 puted revised elements of this comet, from Johannes- 

 burg observations on January 23 and 30, and Feb- 

 ruary 5. 



T :=i92i October 2640738 G.M.T. 

 w = i83°3i' 9-4") 

 0=275° 6' 26-8" -1922-0 

 i '= 32° 56' 6-i" I 

 log ^7 =0-2183570 



The comet was photographed by Prof. Barnard on 

 February 3, when it was of magnitude 10 ; it is now 

 fading. The comet passed perihelion 86 days before 

 discovery, and was fairly well placed for northern 

 observers last autumn, reaching its maximum bright- 

 ness (about 9| mag.) on December i. The fact that 

 it then escaped observation suggests that many 

 comets may pass their perihelion undetected and also 

 that possibly the search for them is not being carried 

 on quite so assiduously as before the war. As the 

 comet is out of reach of European observers and 

 growing fainter, it is useless to give an ephemeris. 



Wireless Time-Signals.— There are four papers 

 on this subject in the January issue of the Mon. 

 Not. R.A.S., from the Greenwich, Pulkovo, Uccle, 

 and Edinburgh observatories. Prof. Sampson, in 

 the last-named paper, brings out the facility which 

 these signals afford for determining the errors of the 

 individual time-determinations, for the mean of them 

 all may be assumed to be a satisfactory datum-line. 

 He gives curves of the errors, which demonstrate the 

 curious fact that each observatory is liable to be in 

 error by as much as 0-2 sec, and that the error frequently 

 persists for some weeks in the same direction. The 

 cause is obscure ; lateral refraction, due to dis- 

 symmetry in the distribution of atmospheric pressure 

 is examined but is insufficient to explain the whole 

 anomaly. Prof. Sampson infers that the observations 

 throw grave doubts on the exactitude of accepted 

 longitude results, which generally rest on special 

 observations made during limited periods. It seems 

 likely that better results may be obtained by using 

 the whole of the clock comparisons made by wireless 

 over periods of several years. Under the old method 

 of observing, personal equation necessitated inter- 

 change of observers, but with the travelling-wire 

 method the difference of observers is reduced to 

 vanishing point. There are two precautions to be 

 observed : first, the time-signals, which are neces- 

 sarily made with a predicted value of clock-rate, 

 must be corrected by later observations at the sending 

 observatory ; secondly, the same system of R.A. 

 of clock stars and mean sun must be employed at 

 both stations ; it may be pointed out that the 



NO. 2735, VOL. 109] 



Connaissance des temps value of the R.A. of mean 

 sun (used at Paris) differs by o-o6 sec. from the value 

 in the Nautical Almanac ; the former uses Le Verrier's 

 solar tables, the latter Newcomb's. 



Stars of the /3 Canis Majoris Type. — 'The 

 Journal of Royal Astronomical Society of Canada for 

 February contains a study of these stars by F. 

 Henroteau. They were at first supposed to be 

 simply spectroscopic binaries, with periods of 3 to 6 

 hours ; but the author expresses doubt as to whether 

 this is the true explanation of the changes of wave- 

 length, as the amplitudes, shape, and periods of the 

 velocity curves all show variations, as do also the 

 widths and intensities of the spectral lines. A list 

 is given of 24 stars suspected to be of this type : one 

 of them is 12 Lacertse, which Prof. Guthnick has 

 investigated with the photo-electric photometer 

 at Babelsberg, finding a small light-variation in the 

 same period as the change of radial velocity. The 

 suggestion is made that they may be binaries in 

 course of formation, rotating Jacobian ellipsoids, 

 or binaries disturbed by a third companion. The 

 stars are nearly all of type B, which is the type where 

 Dr. Jeans found that fission is most likely to take place. 



Spectroscopic Parallaxes with Objective 

 Prism Spectrograms. — It has been thought that slit 

 spectrograms on a large scale were necessary for the 

 determination of spectroscopic parallaxes, but Dr. 

 Harlow Shapley and Mr. Bertil Lindblad show in 

 Harvard College Observ. Circ. No. 228 that good 

 results can be obtained using the large stock of 

 objective prism spectrograms available at Harvard. 

 The pair of lines most used are 4215 (ionised strontium) 

 and 4326 (iron) ; use was also made of the cyanogen 

 bands and the lines of hydrogen, calcium, and 

 manganese. The research is at present limited to 

 naked-eye stars of types Ko to K2. A list of fifty- 

 parallaxes is given ; the largest being X Sagittarii 

 0-113", and 5 Leporis 0-091" (this large value accords 

 with its proper motion of 0-696"). The probable 

 error of a deduced absolute magnitude is of the 

 order of 0-3 mag., which is satisfactorily small. 



The Sun's Rotation from Spectroheliograms. 



The spectroheliograms used in this investigation^ 

 were taken at the Yerkes Observatory between 1903 

 and 1909 by Prof. Philip. Fox, Director of the Dear- 

 born Observatory. The conversion into heliographic 

 longitude and latitude was effected graphically, the 

 image being projected by a lantern on to a globe 

 marked with circles and tilted into the requisite 

 position. The following formulae were deduced for f, 

 the mean daily motion : — 



Northern hemisphere . ^= ii°-i07-l-3°-449 cos'* </>. 

 Southern ,, . f = i2°-i43 + 2°-4o8 cos* ^. 



The differential motion of flocculi round spots is 

 investigated, and is found to indicate an anticy clonic 

 whirl, i.e. opposite to the rotation of the sun on its 

 axis, in the case of single spots, while it is cyclonic 

 round the leading spots of bipolar groups. 



A diagram is given comparing Fox's results with 

 those of other observers. It shows that the angular 

 speeds of the following classes of objects form an 

 ascending series, the increase from first to last being 

 about 1° per day: Reversing layer, Sun-spots, 

 Faculae, and Flocculi (present work), X4227 (Adams), 

 Ha (Adams). 



' Publications of Yerkes Observatory, vol. iii. part 3. 



