October 21, 1915] 



NATURE 



209 



variables on which the result depends. The process 

 cannot supply any new facts. We only get out what 

 put in, but this is generally in a much more 

 iseful form than the original assumptions. It is 

 be hoped that a study of Prof. Buckingham's 

 pers may lead to a diminution of the mass of un- 

 urarrantable deductions and unsound formulae that 

 iW finds its way into scientific and more especially 

 iechnical literature. We need only instance the rule 

 t "no purely arithmetical operator such as log 

 r sin can be applied to an operand which is not a 

 ure number," as one of the laws which is most often 

 overlooked. 



The leading article in Engineering for October 15 

 discusses the second and final report, just issued, of 

 the Departmental Committee on bulkheads and water- 

 tight compartments presided over by Sir Archibald 

 Denny. The report deals with passenger steamers 

 trading to the Continent between the limits of Brest 

 nd the Elbe, in the channels surrounding the British 

 [sles, also those plying on short excursions round the 

 coast, and on rivers, estuaries, lakes, and canals. 

 The fundamental principle underlying the recom- 

 mendations is the same as that in the first report 

 lealing with ocean-going vessels. A difficulty arises 

 dealing with the classes of ship to which the second 

 port refers, owing to the overlapping in the principal 

 tures of design of the respective types; also the 

 s of vessels vary greatly. These considerations 

 ivolved difficulty in stringently applying rules general 

 all types. It seems probable, however, that the 

 neral recommendations of the committee will be 

 eptable to all ; no doubt the exceptions will be 

 sidered on their merits by the authorities. It is of 

 terest to note that Channel steamers are treated 

 or^ severely than oversea passenger steamers in the 

 tter of bulkhead doors — doors worked from the 

 dge alone are permitted. 



Mr. John Murray's new announcements include : — 

 egetable Fibres, by Dr. E. Goulding (in the " Impe- 

 1 Institute Handbooks ") ; A History of the Gold 

 st and Ashanti from the Earliest Times to the 

 ginning of the Twentieth Century, by W. W. 

 aridge, 2 vols. ; and new editions of The Study of 

 imal Life, by Prof. J. Arthur Thomson, illustrated, 

 d Geometry : an Elementary Treatise on Theory 

 d Practice, by S. O. Andrew. 



OUR ASTRONOMICAL COLUMN. 



Jelenium Cell Photometry of S Orionis. — Some 



\ars ago Prof. Joel Stebbins announced that 



asures of the light of 8 Orionis by means of the 



'rnium photometer indicated that this remarkable 



liar system was also an eclipse-variable, although 



ual observation had failed to establish any altera- 



..ju of magnitude. An extensive series of measures of 



the feeble fluctuations of its light was secured during 



the years 1910-11-12 {Astrophys. Journ., September). 



The only spectroscopic orbit then available was Hart- 



mann's memorable determination which revealed the 



first example of fixed calcium lines. These elements 



fere used in deducing the light-curve, but the com- 

 NO. 2399, VOL. 96] 



plete discussion was held up whilst Prof. R. H. 

 Curtiss re-investigated the radial velocity variations, 

 and these new elements have been employed in the 

 discussion of the dimensions of the system. The 

 variation of brightness is only o-i5m., of which oo8m. 

 is considered due to eclipses. The presence of a 

 resisting medium such as the calcium envelope sug- 

 gested by Hartmann's discovery would help to 

 explain the brightness near periastron, which is a 

 feature of the light-curve. It is only possible to fix 

 limitrfor the dimensions of the system. The rninimal 

 values possible for the radii of the two bodies are 

 5 times and 14 times solar, and the mean density 

 of the system is found to be 0006 solar. 



The Plane of the Solar Motion. — Criticism of the 

 hypothesis of star-streaming has led to several attempts 

 to develop a gravitational idea of the stellar universe. 

 Thus Prof. H. H. Turner, in 1912, and just about a 

 year earlier Prof, von S. Oppenheim, both suggested 

 that stellar motions were orbital in character, the stars 

 oscillating or revolving about an ideal centre distant 

 from the sun. The solar system itself contains a 

 model closely representing Prof. Oppenheim 's concep- 

 tion in the swarm of minor planets viewed from the 

 earth. This fact has again been made of use in an 

 investigation of the solar motion (No. 4813, Astro- 

 nomische Nachrichten), affording means of testing 

 the formulae employed in deducing the plane of the 

 sun's path from astrometric data by permitting a 

 determination of the known plane of the earth's orbit 

 from the geocentric movements of the minor planets. 

 Ephemerides of 265 minor planets gave mean motions, 

 etc., of the bodies comprised in every two hours of 

 R.A. Reduction by the Bessel-Kobold method hence 

 gave twelve pairs of values of the position of node 

 and inclination of the earth's orbit; eleven showed 

 fair agreement, and yielded the highly satisfactory 

 mean values ^ = o°44', 1 = 22° o', instead of o" and 23° 27' 

 respectively. The application to the case of the solar 

 motion was made on the basis of data from Charlier's 

 second memoir. The resulting mean values for all 

 Charlier's areas taken together were ^=234° 45' 

 and 1 = 50° 15', corresponding solar apex R.A. 267° 58', 

 declination -f 31-56; whilst for the galactic areas con- 

 sidered apart the mean values were ^ =245° 30' and 

 t = 58° 25', apex R.A., 261° 4', declination, -f 23° 27'. 

 Charlier's values were based, it may be recalled, on 

 the proper motions in the P.G.C. of Boss. 



Displacement of Photographic Stellar Images. — 

 A curious announcement by M. J. Comas Sola (Astr- 

 Nach., 4814) states that among the stars recorded in 

 successive slightly displaced exposures on the same 

 plate and stellar region, occasionally some pairs of 

 images indicate considerable real or apparent move- 

 ment in the corresponding star. An example is given. 

 It is added that it is extremely rare that such a dis- 

 placement appears twice in the same star. 



The Solar Eclipse, August 21, 1914. — Prof. 

 Stormer, together with several colleagues, went to 

 Vefsen to observe the eclipse (Vid. Selk. Fork., 

 No. 5, 1915, Christiania). The observers took up 

 stations at Laksfors and 35 km. to the so«th at 

 Svennigviken, prepared to secure, should the oppor- 

 tunity arise, parallax photographs of aurorae. 

 Favoured by fine weather and clear skies, unfor- 

 tunately no aurorae were seen, but the cameras were 

 used in taking a large number of snapshots of the 

 corona, including seventy exposures with a kinemato- 

 graph. Considering the extremely small scale of the 

 pictures, the form of the corona is very well shown 

 in the reproductions. 



