May 19, 192 1] 



NATURE 



2>1l 



a number of microscopes both large and small, and a 

 long list of object-glasses, eye-pieces, condensers, etc. 

 The astronomical section (No. III.) describes numerous 

 telescopes of different types and a very varied collec- 

 tion of eye-pieces. Section VII. is devoted to what 

 may be termed academic physical apparatus, and 

 Section X. to photographic apparatus. The book list 

 (Section XI.) includes a number of books and journals, 

 among which we notice vols, xxviii.-civ. of Nature. 



Messrs. G. Bsll and Sons will publish next month 

 " Motya : A Phoenician Colony in Sicily," by Joseph 

 I. S. Whitaker (of Malfitano, Palermo). Motya was 

 one of the latest sites occupied by the Phoenician 

 colonisers of Sicily. Though its exact position was 

 long a matter of doubt, it is now identified by archaeo. 

 logists with the small island of San Pantaleo at the 

 north-west extremity of Sicily. Recent excavation 

 undertaken by its owner, Mr. Whitaker, has con- 

 firmed this conclusion, and the forthcoming volume 

 contains a detailed account of his discoveries. 



In a paper entitled " Studies on Phototropism in 

 Solution," part i. (Journ. Amer. Chem. Soc, vol. xliii., 

 192 1), Prof. B. K. Singh indicates some interesting 

 cases of phototropism in solution which he is inves- 

 tigating, and points out that his preliminary results 

 do not fall into line with Senier and Shepheard's 



explanation that phototropic transformations are due 

 to extramolecular rearrangements. 



Under the title Dactylography a bimonthly maga- 

 zine is to appear on July i. It will deal chiefly with 

 the evidence for criminal and other identifications by 

 means of finger-prints; but attention will also be 

 given to a study of the detective aspects of footprints, 

 tattoo marks, deformities, and related matters. The 

 magazine will be conducted by Mr. Henry Faulds, 

 Regent House, Hanley, Stoke-on-Trent. 



Mr. F. Edwards, 83 High Street, Marylebone, 

 W.I, has issued at an opportune moment an interest- 

 ing catalogue (No. 413) of nearly four hundred entries 

 of books, manuscripts, letters, documents; and en- 

 gravings relating to Napoleon and his times. Many 

 choice works are offered for sale. The list can be 

 obtained free of charge. 



Mr. p. Bruce White directs attention to a mis- 

 interpretation indicated by a sentence in the article 

 on researches on bee disease in the issue of Nature 

 for April 28, p. 284. Instead of "The tracheae be- 

 come darkened and ultimately black by the increasing 

 deposition of chitin," it should read: "... by the 

 increasing amount of faecal matter deposited bv the 

 mites." 



Our Astronomical Column. 



Comets. — A new comet 1921c was discovered by 

 M. Dubiago, Petersburg, on April 29. The follow- 

 ing orbit has been received by telegram : — 



T = i92i May 7-611 G.M.T. 

 o) = 104° 45' 

 r^= 66° 4' 

 / = 21° 42' 

 log g =0-02731 



Ephemeris for Greenwich Midnight. 



R.A. N. Decl. Log r 



Log A 



May 



Herr Reinmuth, of Konigstuhl, obtained a twelve- 

 minute exposure plate of Reid's comet on April 30. It 

 shows a faint tail 40' long in P. A. 266°, slightly curved 

 at its extremity towards smaller P. A. There is also a 

 group of short streamers with centre in P. A. 225°. 



Corrections to the ephemeris of Pons-Winnecke : — 

 May 22, -3i^m., -1° o' ; May 26, -45m., -5'; 

 May 30, -59m., +1° 43'. It is a curious coincidence 

 that the three comets now visible are all circumpolar, 

 and their perihelion distances are nearly equal, all 

 being slightly in excess of unity. 



Mr. Denning writes that on April 10 Winnecke's 

 comet was an easy object in a 6|-in. refractor, power 

 about 20. The comet was estimated to be about 9th 

 magnitude, and some 5 or 6 minutes of arc in dia- 

 meter, though it was difficult to define exactly the 

 outer faint limits of the nebulosity. As the comet is 

 brightening, it should become rather conspicuous even 

 in small telescopes after the present moon has left the 

 evening sky, on about May 25. On that date the comet 

 will be 17 millions of miles from the earth, and its posi- 

 tion in the heavens will be two degrees south of S Cygni. 



NO. 2690, VOL. 107] 



It is travelling rather swiftly to the south-east, and on 

 May 30 will be eight degrees south-south-east of 

 o Cygni. It will then probably be about 7th magni- 

 tude, but many comets vary in their light in an in- 

 explicable manner. 



The Eclipsing Variable U Cephei. — The study of 

 eclipsing variables, from which a large amount of 

 information on the sizes, densities, and brightness of 

 the components may be gained, played a large part in 

 the development of the theory of giant and dwarf 

 stars. It is therefore not surprising that Mr. R. S. 

 Dugan, one of the assistants of Prof. H. N. Russell 

 at Princeton, has produced a monograph on U Cephei. 

 The eclipse of the primary star (which is of type Aj) 

 is total, so that we get the spectrum of the secondary 

 isolated. Miss Cannon has recently determined its 

 type as K,. Since this is the larger star, but the less 

 luminous, both would appear to be in the giant stage. 



The light-comparisons were made visually, and in 

 the course of them reason was found to suspect the 

 variability of B.D. 8127° and 8130°. The secondary 

 minimum, being an annular eclipse, gives informa- 

 tion as to the degree of darkening at the limb. In 

 the final elements the limb-light is taken as one-third 

 of that at the centre. The orbit is sensibly circular ; 

 taking its radius as unity, the radii of the stars are 

 020 and 032, and the inclination of orbit plane 864°. 

 The densities are (somewhat conjecturally) given as 

 0-2x4 and 0022 of that of the sun. From asymmetry 

 in the light-curve it is concluded that the bright star 

 rotates more rapidly than the period of revolution, 

 producing a tidal lag of 24°. A further result of tidal 

 friction is traced in the lengthening of the period of 

 variation by 9 seconds in 60 years ; this is indicated 

 with considerable probability by some early observa- 

 tions of magnitude by Schwerd and Carrington. The 

 system thus furnishes an interesting illustration of 

 tidal evolution. 



