674 



NATURE 



[January 20, 192 1 



sol, clear transparent elastic gel, or white opaque 

 solid curd, all at one and the same concentration and 

 temperature. Hitherto the last two types have not 

 been differentiated; probably all previous communica- 

 tions dealt with soap curd, and some confusion has 

 been introduced into the discussion of the nature of 

 gels on this account. Soap sol and gel hav'e been 

 shown to be identical in all respects except elasticity 

 and rigidity, which are characteristic of the gel- form 

 alone. A curd is a sol or gel from which nearly all 

 the soap has been abstracted through the formation 

 of white curd fibres of barely microscopic diameter. 

 These researches, described in the December issue of 

 the Journal of the Chemical Society, have important 

 bearings on the theory of gels, and support the 

 micellar view of Nageli. 



Messrs. J. and A. Churchill announce for early 

 publication a new edition — the eighth — of Lee's 

 ■' iMicrotomist's Vade-Mecum. " It has been prepared 

 by Dr. J. B. Gatenby, who has had the collaboration 

 of several other well-known biologists ; thus Prof. 

 Bayliss contributes a chapter on the theory of dyes 

 and staining. Dr. Da Fano has recast the chapters 



t)n neurological methods. Dr. A. Drew has written a 

 chapter on protozoologlcal techniques. Dr. W. Cramer 

 and the editor a section dealing with the fatty 

 ■substances, the chapter on bone and teeth has been 

 revised by Dr. J. T. Carter, and sections on mito- 

 chondria, Golgi apparatus, fat and yolk, chromatin, 

 chromosomes and nucleoli, embryology, microchemical 

 tests, colloid intra-vitam dyes, . and tissue culture 

 methods have been contributed by Dr. Gatenby. 



•We have received a cc^y of the new edition of its 

 catalogue of second-hand scientific instruments from 

 the firm of Charles Baker, of 244 High Holborn, 

 VV.C.i. It is divided into twelve sections, each of 

 which deals with a particular class of apparatus. 

 Prominent sections are those devoted to microscopes, 

 surveying instruments, physical apparatus of various 

 types, and photographic material. That on micro- 

 scopes contains some seventy items, ranging from 

 single sliding-tube instruments to those carrying all 

 the modern improvements. The firm has also a 

 number of second-hand scientific books and periodicals 

 for sale, including collections of various journals of 

 microscopy and Nature, vols, xxviii. to civ. 



Our Astronomical Column. 



.\pproaching Return of Pons-Winnecke's Comkt. 

 —Among the periodical comets due to return this 

 year that of Pons-Winnecke presents the most 

 interesting possibilities. The comet will be near the 

 earth at the time it arrives at perihelion at about the 

 end of June or early in July next, and as its orbit 

 lies verv near that of the earth a meteoric shower 

 seems highly probable. 



The first abundant exhibition of meteors from this 

 source appears to have taken place on June 28, igi6, 

 when it was witnessed by Mr. W. F. Denning at 

 Bristol, who pointed out in Nature of July 27 of that 

 year the significant resemblance of orbit betv^een the 

 meteors and Pons-Winnecke's -comet. \ 



The last return of the comet to perihelion occurred 

 on September i, 1915, and, the shower of meteors 

 having been observed at Bristol ten months later, the 

 stream must be fully 600,000,000 miles long. If the 

 display should fail to be visible at the end of June 

 next it should certainly return next year. 



The radiant point is situated a few degrees north- 

 east of the star Eta in Ursa Major, and the radiation 

 appeared to be very diffused in June, 1916, so that it 

 was difficult to ascertain the exact centre. In former 

 years the comet of Pons-Winnecke was always suffir 

 ciently distant from the earth to escape contact of 

 its niaterials with our atmosphere, but during the 

 last half-century the planet Jupiter has materially dis- 

 turbed its orbit, and brought that section near peri- 

 helion extremely close to the earth. 



Stellar Parallaxes. — Yerkes Observatory Publica- 

 tions, vol. iv., part 3, contains parallaxes of fifty-two 

 stars obtained photographically with the g^reat Yerkes 

 refractor by Mr. G. van Biesbroeck and Mr. H. S. 

 Pettit. A yellow colour-filter was used, and the 

 bright stars Were cut down 6 mags, or thereabouts 

 bv a double rotating sector. The stars are partly 

 fundamental ones, partly faint stars with large p.m. 

 The following are some of the more interesting 

 results :^Aldebaran 0047'', Castor 0059", Procyon 

 0-307", B.D. +67552° oioe" (this is the first deter- 

 mination made for' this star), Lai. 21 185 0382', ^ Her- 



NO. 2673, VOL. 106] 



culis 0095", Barnard's p.m. star 0509', and Vega 

 01 14". The average probable error is o-oio". 



Two more Publications of the Allegheny Observa- 

 tory (vol. v., Nos. 4 and 5) have been received, and 

 contain parallaxes of eighty stars, many of them 

 now determined for the fi/st time. The average 

 probable error is 0008". There are only two paral- 

 laxes exceeding 01", viz. Pi II. 123 0145"' and O.A.N. 

 21338 0134" (first determination). Other interesting 

 stars are aTrianguli 0-045", SCephci 0006", 54 Piscium 

 0096", /SAndromedse 0033", Furuhjelm's companion 

 to Capella 0-071" (this is easier to measure than 

 Capella itself, and from the common p.m. the paral- 

 lax must be appreciably the same), i; Geminorum 

 0-016", Lai. 33439 0095" (.Adams and Joy found 

 0087" spectroscopically), and Pi XXIII. 218 0-092'. 



Catalogue of Nov^. — ^The Japanese AstronomicaX 

 Herald for October, 1920, contains a very useful cata- 

 logue of novae, giving their R..^. and decl. for 

 1900, the date of outburst, and other particulars. 

 Tycho Brahe's star of 1572 is No. 1, and Mr. Denning's 

 nova of la* August No. 41. The average in the 

 last thirty years has been just one per annum. The 

 nova of 1885 in the Andromeda nebula and the other 

 faint novae recently detected in spiral nebulae have not 

 been included in the list. The galactic co-ordinates are 

 fjiven, and the distribution of novae in the four quad- 

 rants is as follows : 



Galactic Long. No. of Novx 



0° to 90° 14 



'90° to 180° 8 



180° to 270° 3 



270° to 360° 16 



The deficiency in the third quadrant does not seem 

 to be explicable as a result of south declination, for 

 there are practically as many stars south of the 

 equator as north of it (twenty to twenty-one). There 

 are fourteen stars south of decl. —20°, which is the 

 full number to be expected in this zone, one-third of 

 the whole sphere. Hence the unsymmetrical dis- 

 tribution gives some grounds for conjecturing that the 

 galaxy may be nearer to us in the first and fourth 

 quadrants. 



