192 



NATURE 



[May 9, 1918 



and on the latent heat of vaporisation of the liquid. 

 The heat in each case is supplied electrically, and the 

 change of temperature measured by means of a plati- 

 num resistance thermometer. Under saturation condi- 

 tions the specific heat of the liquid varies from i-o6 

 calories per gram at —40° C. to i-io at 0° C. and 

 to I -16 at 40° C. The heat measured in joules per 

 gram, which must be abstracted from the liquid, 

 when the pressure is increasedbyakilogramper sq. cm. 

 in order to keep the temperature constant varies from 

 o-o6 at —40° C. to 009 at 0° C. and to 015 at 40° C. 

 The latent heat of vaporisation in calories per gram 

 varies from 332 at —40° C. to 302 at 0° C. and to 

 263 at 40° C. It is to be hoped that these results will 

 soon be made available to refrigeration engineers in 

 the form of a total heat-entropy chart. 



A SIMPLE chart for the conversion of temperatures 

 from the Fahrenheit to the Centigrade scale, or vice 

 versa, has recently been issued by the Cambridge 

 Scientific Instrument Co., Ltd. The device consists 

 of the two scales side by side in the form of a spiral, 

 and is printed on a card about i ft. square. The 

 effective length of the scales is thus about 6 ft., thereby 

 permitting the divisions, which correspond with 2° 

 each, to be satisfactorily open without at the same 

 time restricting the range. This covers from the 

 absolute zero, —273° C, to 2000° C. Both the 

 Fahrenheit and Centigrade scales are divided to 2° to" 

 prevent confusion, and each interval of 10°, 50°, and 

 100° is clearly marked to facilitate easy reading. The 

 chart should prove of service to all users of pyro- 

 meters or other temperature-measuring instruments, 

 as both scales are so generally employed that con- 

 version from one to the other cannot in practice be 

 avoided. In addition to the conversion chart, tables 

 of useful thermometric data are given. The Cam- 

 bridge Scientific Instrument Co. states that it 

 will be pleased to forward a copy of this chart free 

 of charge to anyone interested on receipt of six penny 

 stamps to cover the cost of postage. 



The report of the National Union of Scientific 

 Workers for the quarter ending March 25 last out- 

 lines the progress which has been made with the 

 work of organisation of the society. Eight branches 

 of the union have been definitely formed in various 

 parts of the country, the prospective membership of 

 which appears to be between 300 and 400. An 

 organising sub-committee is being set up to deal with 

 the London area, which, the report says, presents 

 special difficulties. Among the aims of the union 

 specified in the report is the maintenance of the free- 

 dom and independence of research. All inquiries 

 respecting the work of the union should be addressed 

 to the secretary, Mr. Norman Campbell, North Lodge, 

 Queen's Road, Teddington. 



A NEW series of books on industrial chemistry, 

 edited by Dr. S. Rideal, is announced by Messrs. 

 Bailliere, Tindall, and Cox. It is intended to give 

 in it a comprehensive survey of the chemical indus- 

 tries. Two volumes have just been issued. " Indus- 

 trial Electrometallurgy," by Dr. E. K. Rideal, and 

 "The Application of the Coal Tar Dyestuffs," by 

 C. M. Whittaker, are in the press. Further volumes 

 will deal with "The Industrial Gases," "Silica and 

 the Silicates," "The Rare Earths and Metals," "The 

 Iron Industry," "The Steel Industry," "Gas-works 

 Products," "Animal Proteids," "Organic Medicinal 

 Chemicals," "The Petroleum Industry," "Fats, 

 Waxes, and Essential Oils," "Synthetic Dves," 

 "Wood and Cellulose," "The Carbohydrates," and 

 " Rubber, Resins, Paints, and Varnishes." 



NO. 2532, VOL. lOl] 



The April issue (No. 64) of Mr. C. Baker's Classified 

 List of Second-hand Scientific Instruments has just 

 reached us. In consequence of the increasing difficulty 

 in obtaining new apparatus, it should be of especial 

 interest and service to scientific workers. Copies can 

 be had upon written application to 244 High Holborn,. 

 W.C.I. 



Messrs. Dulau and Co., Ltd., 37 Soho Square,. 

 W.I, have just issued a Catalogue (No. 72) of 764 

 books — some scarce — on botany and horticulture,, 

 anthropology, ethnology, archaeology, scientific travel, 

 etc. The list will doubtless be interesting to many 

 readers of Nailkk. 



OUR ASTRONOMICAL COLUMN, 



Photographs of the Spectrum of Venus. — In a 

 recent report to the Royal Astronomical Society 

 (Monthly Notices, vol. Ixxviii., p. 278) Mr. J. Evershed 

 gives a preliminary account of some photographs of 

 the spectrum of Venus which have been obtained with 

 the large, grating spectrograph at Kodaikanal. The 

 primary purpose of the investigation was to ascertain 

 whether the general shift of the lines towards the red 

 at all points on the visible disc of the sun affects also 

 a hemisphere turned 90° or more from the earth. 

 If the wave-lengths in the light from Venus, after 

 correction for the motion of the planet as a whole, are 

 found to be identical with those from ordinary sun- 

 light, the solar displacements cannot be attributed solely 

 to motion of the absorbing gases; but if the Venus 

 spectra show a smaller wave-length, a general motion 

 of the solar vapours away from the earth may reason- 

 ably be inferred. Five good photographs, with iron 

 arc comparisons, were obtained in October, 19 17, 

 which agree with a previous series of plates taken 

 during February, 1917, in showing a distinctly smaller 

 wave-length for iron lines in the spectrum of Venus 

 as compared with the corresponding lines in the con- 

 trol spectrum of daylight. The results thus favour the 

 motion interpretation of the solar shifts, involving an 

 earth effect; but as the February plates were possibly 

 not entirely free from pole effects in the arc, con- 

 firmatory evidence will be sought during June and 

 July next. The trustworthiness of the plates for the 

 purpose in view is indicated by the fact that the com- 

 bined results from the east and west elongations yield 

 a value for the solar parallax which differs only very 

 slightly from that adopted in the Nautical Almanac. 

 Only, one plate was obtained when the planet was at 

 half phase or less, but this is of special interest as 

 showing a discrepant velocity, which is difficult to 

 account for except by supposing that Venus rotates in 

 the same direction as the earth and with the same 

 order of velocity. It is further expected that the 

 Venus plates will eventually decide whether the sun's 

 gravitational field is concerned in the solar line-shifts 

 or not. 



Radial Velocities by Objective Prism. — ^The great 

 advantages offered by the objective prism in the photo- 

 graphy of stellar spectra have led to numerous at- 

 tempts to utilise this instrument for the determination 

 of radial velocities. The spectra of stars down to the 

 tenth and eleventh magnitudes can be photographed 

 in this way, and since a great number of spectra 

 appear on a single plate, even an approximate method 

 of deriving radial velocities would clearly be of great 

 value in connection with the problems of stellar 

 motions. One of the most promising methods appears 

 to be that suggested by Prof. R. W. Wood, in which 

 the light from the stars is passed through a filter of 



