April i, 1920] 



NATURE 



149 



of 8 or 9 to I is not exceeded in naval practice of 

 moderate and high power. Of the 556 sets in ser- 

 vice, some extending up to nearly six years, it has 

 only been necessary to remove three for refit due to 

 misalignment; no actual breakdown occurred, and the 

 i^ears, after dressing up, were afterwards re-utilised. 



iTwo cases of fractured teeth occurred ; the broken or 

 cracked portions were removed and the damaged teeth 

 I were smoothed up. There is a great saving in the 

 blading of the turbine by the adoption of mechanical 

 ;4caring:, amounting in the case of a destroyer to 

 70,000 ft. of blading in a direct drive, against 7720 ft. 

 in the geared drive. The increase in efficiency is 

 161, 17, and 20 per cent, respectively for light 

 (ruisers, flotilla leaders, and torpedo-boat destrovers 

 It full power; at one-fifth power the increases in 

 llkiency are 16-5, 20, and 20 per cent, respectively. 



Messrs. Thom.as Murby and Co. are publishing 

 •shortly two books likely to interest geological readers, 

 \ iz. "An Introduction to Palaeontology," by Dr. 

 A. Morley Davies, and " Petrographic Methods and 

 Calculations," by Dr. A. Holmes. In the first-named 

 work the "type-system" of Huxley is applied. A 

 limited number of fossil species are described in 

 detail, the relation of the structure to the anirnal's 

 mode of life being pointed out, as well as the effects 

 of fossilisation. Each such description is followed 

 l)y a general account of the group of which the 

 "type" is representative. The volume will contain 

 appendices dealing with rules of nomenclature and 

 methods of extracting and preserving fossils. 

 In Dr. Holmes's volume the following subjects 

 receive attention : Specific gravity and porosity of 

 rocks — examination of crushed rocks and loose sedi- 

 ments — mineral analyses by heavy liquid, magnetic, 

 and electrostatic methods — mechanical analysis of 

 sands — preparation of thin sections and their examina- 

 tion by staining, micro-chemical, and other methods 

 — chemical analyses of rocks and their interpretation 

 — representation of analyses by diagrams — suggestions 

 for the description of rocks. 



Messrs. W. Heffer and Sons, Ltd., Cambridge, 

 have just circulated a miscellaneous catalogue (No. 186) 

 of secondhand books which will doubtless be of 

 service to man^- readers of Nature. The more strictlv 

 scientific portion contains 100 items ranging over 

 most of the branches of scientific knowledge ; a 

 lengthier section gives particulars of works on folk- 

 lore, mythology, psychical research, comparative 

 religions, etc. The Sanskrit collection of the late 

 Dr. A. F. R. Hoernle, comprising about 400 volumes, 

 is also listed. The catalogue may be had upon 

 .i|)plication. 



Readers of Nature interested in biography and 

 (Itsirous of obtaining books relating to this subject 

 at small cost should obtain a copy of Catalogue 

 No. 400 just issued by Mr. F. Edwards, 83 High 

 Street, Marylebone, W. i. The list is not particularly 

 strong in science, but it contains lives of Charles 

 Darwin, Sir Joseph Banks, J. J, Audubon, Thomas 

 l?ewick, Sir Colin Scott-Moncrieff, and others. There 

 is also a section of works on genealogy and familv 

 liistory. The catalogue will be sent on request. 

 NO. 2631, VOL. 105] 



Our Astronomical Column. 



April METEORS.-Of April generally and its special 

 meteoric display it can scarcely be said that thev often 

 possess features of striking interest from a spectator's 

 point of view The fact is that the spring, months 

 are usually all deficient in abnormal phenomena of 

 tnis kind, and observers are sometimes sadlv dis- 

 appointed with the result of their observations •' for if 

 meteors from Lyra are absent or few, there is little 

 else to engage the student, as meteors mav fall not 

 more abundantly than three or four in an hour, 

 .u T ■'^•i^''^ periodic returns of grandeur attached to. 

 the Lvrids, but the uncertainty of the periodic time 

 renders it a non-predictive feature. Hence the ob- 

 server must needs take up his stand with a verv 

 doubtful prospect before him. 



But the stream of Lyrid meteors has important 

 historical associations, and the shower can boast of a 

 known cometary parentage. These facts, combined 

 with the possibility of a bright and abundant displav 

 in any year, lure observers to look for it with ah 

 interest and anticipation sometimes amply justified. 

 Spectrum of »jArgus.-As Mr. Baxandall and 

 Miss Cannon suspected changes in the spectrum of 

 this interesting star. Dr. Joseph Lunt took two photo- 

 graphs in February and April, 19 19. Each was ex- 

 posed on three nights with a total exposure of nine 

 hours. The spectrum consists mainly of bright lines - 

 there are dark lines, but they cannot be identified 

 with known lines, and mav be merely interspaces 

 between bright bands. The "results for radial motion 

 differ according to the lines employed. The enhanced 

 iron lines give -307 and -282 km. /sec. from the 

 two plates. The chromium lines are in fair agree- 

 ment with this, but the hvdrogen bright lines give 

 + 46-5 and -I- 487 km. /sec, a difference of 77 km. /sec 

 from the other lines. On the other hand, hvdrogen 

 dark hnes give -19 excluding H^, or -33 including it. 

 Dr. Lunt suggests in explanation the settling down 

 of an extensive outer hydrogen atmosphere on to the 

 central body. He refers to Mr. Innes's discoverv of 

 a faint companion, and notes that hitherto no certain 

 sign of variable radial velocity has been detected. 

 He emphasises the importance"^ of keeping the star 

 under constant watch, both visual and spectroscopic, 

 as the light curve gives expectation of another 

 brightening about the present time. The star is a 

 curious link between novag and variables. Miss 

 Cannon noting a strong resemblance between its 

 bright-line spectrum and that of Nova Auriga on 

 1892 February 17 (Monthly Notices, vol. Ixxix.). 



Infra-red Spectra of Nebula.— Investigations are 

 being carried out at the Lick Observatory by Dr. K. 

 Burns with the object of securing photographic plates 

 of great sensitivity to infra-red radiations, and some 

 plates prepared by him have been utilised by Mr. 

 W. H. Wright for exploring the, spectra of nebulse 

 in this region. In the Publicat'ions of the Astro- 

 nomical Society of the Pacific, No. 185, Mr. Wright 

 gives an account of his preliminarv attempts in this 

 direction, with the results obtained in the case of the 

 planetary nebula N.G.C. 7027. The 36-in. refractor 

 of the Lick Observatory was used with a single- 

 prism spectrograph giving the rather small dispersion 

 of I mm. to about 600 A.U. on the plate. The focus 

 was not good in the region required, but fair defini- 

 tion was obtained between A 6700 and A 8500, and 

 his photographs show four lines in the extreme red 

 not previously reported. The corrected wave-lengths 

 are given as approximately 7009, 7065, 7138, and. 

 7325. and in addition to these lines there are others at 

 A 6678 and A 6730 which have been measured previously 

 with other apparatus 



