56o 



NATURE 



[July i, 1920 



tigated, and the other with the solvent alone. Owing 

 to the opposing action of the two prisms the disper- 

 sion of the solvent is thus eliminated, and the 

 anomalous dispersion of the solute observed directly- 

 By this means the authors have determined the indices 

 of refraction of the materials as follows : — Methyl- 

 violet for wave-length 6712, 2-52; 6497, 2-43; 4455, 

 1-23; and 4227, 1-45. For fuchsine 6712, 2-21; 6497, 

 241 ; 6170, 263 ; 5857, 278; and 4227, 1-19. For para- 

 nitrosodimethylaniline 6497, 1-74; 6170, 178; 5S57, 

 i-8i; 5603, 1-85; and 5270, 1-93. 



In the course of an article in Engineering for 

 June 18 on the Birkenhead' shipyard and works of 

 Messrs. Cammell Laird and Co., Ltd., reference is 

 made to the original generating stations which sup- 

 plied the whole of the power for the works. The 

 original station was equipped entirely with gas engines 

 supplied from a Mond plant, which also supplied gas 

 to the furnaces in the platers' and other shops. The 

 ten gas engines were of varying sizes, and had a total 

 capacity of 2500 kw. This gas station has done good 

 service, but the large number of comparatively small 

 gas-driven units has resulted in a considerable main- 

 tenance charge. There has also been difficulty at times 

 during the war in obtaining suitable fuel for the 

 producers. These conditions, combined with agrowing 

 demand for power, have resulted in a decision to shut 

 the gas station down altogether, and to transfer all 

 power generation to the new turbine station. The 

 matter is of some interest in view of the controversy 

 on fuel economy, and illustrates the fact that there 

 are points other than mere economy of fuel to be 

 taken into consideration by large power-users. 



We are asked to state that the Research Association 

 of British Rubber and Tyre Manufacturers has secured 

 laboratory accommodation in the Chemistry Depart- 

 ment of University College, Gower Street, W.C.i. 



We regret to learn from an inset announcement in 

 the current issue of the Scottish Naturalist that, not- 

 withstanding that all editorial work in connection 

 with the journal is rendered gratuitously, there was a 

 loss on the year's working, which, however, has been 

 generously met, and that in consequence of the con- 

 tinued increasing cost of production there is a possibilitv 

 of the magazine ceasing to exist. We trust that this 

 contingency will be averted, for our contemporary has 

 performed valuable services to Scottish natural history 

 for the lengthy period of fifty years. A largely in- 

 creased subscription list would probably save the situa- 

 tion, and the publishers, Messrs. Oiiver and Bovd, 

 Edinburgh, will be glad to have the names of all who 

 will help in the way suggested to keep in circulation 

 this useful scientific periodical. 



The latest catalogue (No. 188) of Messrs. W. Heffer 

 and Sons, Ltd., Cambridge, gives particulars of 

 upwards of 1900 second-hand books ranging over a 

 number of subjects. There are sections devoted to 

 science and mathematics ; folk-lore and mythology ; 

 archaeology; India; Cevlon ; China, Japan, and the 

 Far East ; Turkey, etc. The catalogue, which will be 

 sent free upon request, is worthy of perusal. 

 NO. 2644, VOL. 105] 



Our Astronomical Column. 



Tempel's Seco.nd Periodic Comet. — The only addi- 

 tional information that has come to hand about this 

 comet is that it was of magnitude 11 at the end of 

 May. It should be of magnitude 9 or 10 in July, and 

 therefore visible in moderate instruments. Accurate 

 observations of position are badly needed, as very few 

 were obtained at the last apparition in 1915. " The 

 period of this comet (5J years) is the shortest known 

 except that of Encke. Observations were secured in 

 1873, 1878, 1894, 1899, 1904, 1915, and 1920. The 

 following approximate ephemeris is for Greenwich 

 midnight : 



R.A. S. Decl. Log r Log A 



h. m. s. n , 



July 6 ... 23 14 51 7 17 o-i2i6 9-6962 

 14 ••• 23 39 41 8 59 o-J2i6 9-Mi 



22 ... O 2 40 II 5 0-1236 96685 

 30 ... O 22 24 13 27 0-1274 96636 



Aug. 7 ... o 38 50 16 I 0-1330 96650 



Denning's Comet of 1881 and a Meteoric Shower. 

 — The Rev. M. Davidson has recently made some 

 interesting computations of the dates and radiant 

 points of certain comets if they originate meteor 

 showers. Among these, Denning's comet of 1881 

 indicates a radiant on August 4 at 303°- 10° about 

 3° N. of aCapricorni. For many vears a prominent 

 shovi'er of slow, bright meteors has been visible from 

 this point at the end of July and the early part of 

 August, and it is quite possibly connected "with the 

 comet named. It was well seen in 1900 and 1902, 

 as well as in 1908 and 1916. The comet probablv 

 returned in 1899, 1907, and 1916, though it escaped 

 observation, and the next return should occur in 1925 

 if the computed period of about 8| j'ears is correct. 

 There are, however, meteors every year from this 

 shower in Capricornus, and it should be specially 

 looked for during the period from July 25 to August 8. 



Capture Orbits. — Text-books on astronomy fre- 

 quently contain a good deal of speculation on the 

 possibility of capture of comets and satellites ; we 

 may quote as instances the Leonid meteors, supposed 

 to have been diverted by Uranus from a quasi- 

 parabolic orbit into an ellipse of short period, and the 

 numerous comets of the Jovian family, on which 

 Jupiter is presumed to have exerted a similar influence. 

 In these cases the perturbing planet made the capture, 

 not for itself, but for the sun. Capture of the former 

 sort, in which the planet retains the captured body as 

 a satellite, can apparently take place only with the 

 aid of a resisting medium, in which case we must date 

 the event in remote ages. 



Little research of an accurate numerical character 

 has hitherto been carried out on the subject. Prof. L. 

 Becker contributes two papers to M.N. (vol. Ixxx., 

 No. 6), in which he shows that a star approaching a 

 binary system may in certain cases suffer capture, 

 while one of the original pair may be expelled from 

 the system. He then points out that approaches 

 would be more frequent in the direction of relative 

 motion of the two star-streams, and by analvsis of 

 the distribution of the major axes of the orbits of 

 binaries obtains a result in fair conformity with the 

 theorv. The research is made more difficult by the 

 fact that there are two possible positions of the^ plane 

 of a binarv orbit. In a few cases (notably in the 

 systems of Sirius and a Centauri) the spectroscope 

 has decided which of these positions is the correct one. 

 There are probablv several other systems in which 

 the spectroscope is capable of giving a decision. 

 Observations of this kind are very desirable wherever 

 they are possible 



