838 



NATURE 



[August 26, 1920 



engineers, "free from all bias," to investigate the 

 matter thoroughly on account of its vital importance 

 to the welfare of the uhole country. 



The paper by W. L. Cheney on the measurement 

 of hysteresis values when using- high magnetising 

 forces, which has just been published by the U.S. 

 Bureau of Standards (Paper No. 383), will be of in- 

 terest to all engaged in magnetic research. When 

 employing ordinary methods it is extremely difficult to 

 g-et the accurate values of the remanent induction and 

 the coercive force owing to what has been called mag- 

 netic viscosity. This probably also slightly affects the 

 author's results. His method is a modification of the 

 isthmus method, and consists essentially of a du Bois 

 electromagnet with flat pole-pieces separated by an air- 

 g-ap and pierced coaxially so that a rod may be inserted. 

 The magnetic force and the induction are measured 

 by suitable coaxial test coils. Magnetic forces up to 

 2500 gausses were employed. Quenching eutectoid 

 steel (0-85 per cent, carbon) in oil lowered the remanent 

 induction, but considerably increased the coercive 

 force. Experiments were made on the K.S. magnet 

 steel prepared by Prof. Honda, and the high coercive 

 force of 200 gausses was obtained when the specimen 

 had been magnetised with 800 gausses. 



An uncommon piece of work is described in 

 Engineering for August 13 in the form of a long 

 wooden jib for a derrick crane designed and con- 

 structed for the Admiralty during the war by the 

 Imber Court Engineering Works, Thames Ditton, 

 Surrey. The crane, with a 50-ft. post, had to be 

 capable of raising a 3-ton load up to a platform 

 100 ft. high. The jib was 135 ft. long from the 

 centre of the bottom pin to the centre of the rope- 

 wheel, and the wooden construction adopted resulted 

 in a jib being produced of one-third the weight and 

 having a higher factor of safety than steel would 

 have given. Including the rope-wheel and end casings, 

 the jib complete weighed only 2 tons 13 cwt. The 

 jib was built up of four corner-posts, each post being 

 made of nine laminations of Oregon pine glued 

 together with waterproof glue. The jib was divided 

 into panels by struts, also of Oregon pine, and each 

 panel had diagonal bracing, both longitudinal and 

 transverse ; these bracings were composed of stranded 

 piano-wire. The struts were fixed to the corner-posts 

 by welded steel clamping boxes, to which the diagonal 

 braces were also connected by means of bolts on which 

 the wire was wound. The bolt-heads were formed 

 with teeth, with which two spring pawls engaged, so 

 that turning the bolt tightened the wires and slacking 

 back was prevented by the pawls. 



The concluding volume — the sixth — of the Scientific 

 Papers of the late Lord Rayleigh is to be published 

 by the Cambridge University Press in the spring of 

 next year. It will range over the period 191 1-20. 

 Among the other forthcoming publications of the Cam- 

 bridge University Press is "The Spectrum of Nova 

 Geminorum II.," by F. J. M. Stratton. It will con- 

 stitute vol. iv., part i., of the Annals of the Solar 

 Physics Observatory, and is promised for the end of 

 the present year. 



i\iU. 2652, VOL. 105] 



Our Astronomical Column. 



Discovery of a Nova in Cygnus. — Mr. W. F. 

 Denning, of Bristol, writes that on the evening of 

 August 20 he observed a star previously unknown to 

 him in the northern region of Cygnus. He has made 

 it a . practice during the last few years of carefully 

 searching for these objects while he has been watching 

 for meteors. The object when discerned on August 20 

 was of about 3^ magnitude, and its rough position 

 was in R.A. igh. 56m. and declination 53^° N. It 

 formed a little triangle with the stars V* and d (20) 

 Cygni. On referring to star-charts, etc., Mr. Denning 

 quite failed to identify the object in question, and 

 therefore concluded it to be a new star. 



The position of the nova in the Milky Way is in 

 accordance with past experience, for nearly all past 

 novae have been in the Milky Way or on its borders. 



Mr. Denning saw the present object again on 

 August 21 in the openings between swiftly passing 

 clouds, and it appeared of about the same brightness 

 as on the previous night, but only hurried glimpses 

 were obtainable. 



On August 22 the brightness was estimated = 2-8 

 mag., and on August 23, 2-2 mag., so that its light is 

 increasing. 



Parallax of the B-type Star Boss 1517. — Mr. J. 

 VoCite recently announced a large parallax and proper 

 motion for this star. Mr. A. J. Roy showed, how- 

 ever, that the true proper motion in R.A. was only 

 one-tenth of Mr. Voute's value, being —0-023"; that 

 in declination is +0-129". Mr. •Voute has recomputed 

 the parallax with this value, and finds 0-048", which 

 is in good accord with Kapteyn's hypothetical value 

 0-033". 



The star is one of the nearest of the B stars, being 

 at about the same distance as Achernar. Its chief 

 interest lies in its surprisingly low absolute magni- 

 tude for a B-type star, its apparent visual magnitude 

 being 5-9. According to Mr. R. E. Wilson, of the 

 D. O. Mills Observatory, the radial velocity is 

 -1-102 km. /sec, or +83 corrected for the sun's motion. 

 The position for 1910 is R.A. 6h. om. 59-4365., south 

 decl. 32*^ 10' 10-91". 



Publications of the Astronomical Laboratory at 

 Groningen, No. 29. — ^This is a further instalment of 

 Prof. J. C. Kapteyn's valuable researches on the 

 stellar system. He summarises the large amount of 

 new material that has become available since he first 

 took up the subject, and shows that the time is 

 appropriate for a fresh investigation of the secular 

 parallaxes of stars of different magnitudes and spec- 

 tral classes. The secular parallax is defined as the 

 angle subtended at the star by the unforeshortened 

 annual motion of the, sun. Assuming its speed to be 

 19I km. /sec, then annual parallax:=sec. par. xo-243. 

 The following values are found for the variation of 

 parallax with galactic latitude : From latitude 90° to 

 40°, parallax= 1-17 of mean; from 40° to 20°, 0-96 of 

 mean ; and from 20° to 0°, 0-87 of mean. 



Manv investigators have found discordant values of 

 the declination of the solar apex as derived from stars 

 of different magnitudes. Prof. Kapteyn is inclined to 

 attribute this to imperfect elimination of magni- 

 tude equation in declination from the catalogues 

 employed, since he makes the (Tiscordance verv 

 small. 



Prof. Kapteyn emphasises the importance of 

 separating stars of different spectral type in 

 these investigations. In view of the great 

 range of absolute magnitude according to tyoe, 

 he says that the grouping of all types is like 

 making a single statistical investigation of the 



