January 27, 1910] 



NA TURE 



constants he has based on those observations. If it is 

 assumed that the movements of the granules in such 

 emulsions can be classed with those of the molecules of 

 a gas, the theory of the equal partition of the energy 

 amongst the molecules of mixed gases leads to the con- 

 clusion that the mean kinetic energy of translation of these 

 granules is identical with that of gas molecules. If, then, 

 the kinetic energy of the granules can be determined, the 

 number of gas molecules in a cubic centimetre of gas under 

 normal conditions may be calculated. M. Perrin determines 

 the kinetic energy of the granules in two independent 

 wavs : — first, from measurements of the distribution of the 

 granules at different heights in the emulsion, which he 

 finds follows the same law as in gases ; second, from 

 measurements of the displacements of the granules in a 

 given time, and the law which Einstein has deduced for 

 the connection between displacement and mean kinetic 

 energy. Both lead to the conclusion that the number of 

 molecules in a gram molecule is 7o.5Xio'°. 



Commenting on the death of M. Delagrange, Engineering 

 for January i^ points out two special features of technical 

 interest in this aeroplane accident. In the first place it is 

 the first fatal accid^-nt with a machine of the monoplane 

 type, and, in the second, it is the first which appears to be 

 distinctly owing to a failure in the main structure of the 

 machine used. It seems to have been generally assumed 

 that the biplane is a safer machine than the monoplane, 

 vet the fact remains that the greater number of accidents 

 have happened to the biplane. There seems to be good 

 nason to suppose that the death of M. Delagrange was 

 caused by the main framing forming one of the wings 

 giving way altogether, followed by the fall of the machine. 

 The general construction of the framing is that of a trussed 

 girder constructed of wood and steel wire. The wires are 

 very numerous in the biplane as compared with those re- 

 quired in the monoplane frame. Usually the wire stays 

 are of solid steel wire or ribbon, which gives little indica- 

 tion of readiness to break. Stranded wire rope is better 

 from this point of view, as ample warning is always given 

 by some of the strands breaking before the rope finally 

 gives way. The broken strands are very easily detected. 

 Further, many machines of both types have the spars in- 

 sufficiently stayed or not stayed at all against the longi- 

 tudinal pressure due to the air resistance, which pressure 

 in such cases will be taken up entirely by the spars. To 

 make the aeroplane of practical use, trustworthiness and 

 safety are required, and more attention should be given 

 to these rather than to cutting down structural weights for 

 the purpose of striving after " records." 



The December (1909) number of the Journal of Physical 

 Chemistry contains a series of determinations, by Messrs. 

 O. C. Schaefer and H. .Schlundt, of the dielectric constants 

 of the anh3'drous halogen acids, which gave the following 

 values : — 



HI 217°, 2-90; -50°, 2-88; -70° (solid), 3-95. 



HBr 247°, 3 '82 ; -80°, 6-29. 



HCI 277°. 460; -90°, 8-85. 



HCN ... -25° (solid), 2-4 ; -70° (solid), 3-05. 



.\ttention may also be directed to a paper, by Mr. M. M. 

 Garver, on a kinetic interpretation of osmotic pressure, 

 in which the fundamental assumption is made that, whilst 

 the average velocity of water-molecules in a sugar solu- 

 tion is the same as in pure water at the same temperature, 

 the range of variation on either side of the mean is greatly 

 reduced, so that vaporisation and freezing are alike 

 rendered more difficult. 



NO. 2100, VOL. 82] 



TiiE volume of the Journal of the American Chemical' 

 Society, which has just been completed, is remarkable, 

 not only for the importance of the researches that are 

 described in it, but also for the excellent conciseness with 

 which the results are presented. Two papers by Mr. F. F. 

 Rupert, on the properties of aqueous ammonia and aqueous 

 hydrochloric acid, might be cited as models, not only of 

 accurate and thorough investigation, but of successful 

 resistance to the temptation to expand the bulk of the 

 paper in proportion (or out of proportion, as the case 

 may be) to the importance of the subject. The isolation 

 of ammonium hydroxide, (NHJOH, and of ammonium' 

 oxide, (NH,),0, is recorded, for instance, in a paper which 

 covers less than three pages, and congratulations are due 

 from the reader to authors and editor alike on the excel- 

 lent results that have followed from their cooperation in 

 this respect. The contents of the volume are of such a 

 character as to give much support to the invitation that 

 has recently been extended to English chemists to become 

 members of the American society. 



The Institute of Chemistry has issued a third edition, 

 revised and enlarged, of the " List of Official Chemical 

 Appointments." The list has been compiled by Mr. R. B. 

 Pilcher, registrar and secretary of the institute, and is sold 

 at 2s. net. It is arranged in three main divisions : — 

 appointments in Great Britain and Ireland, under the 

 various departments of State, county and borough councils, 

 and other authorities, together with professorial and teach- 

 ing appointments in schools and colleges in this country ; 

 appointments in India and the colonies ; and an appendix 

 giving information regarding chemical societies and institu- 

 tions. A register of fellows and associates of the institute 

 who are seeking appointments is kept at the office of the 

 institute, so that authorities may obtain the services of 

 qualified professional chemists as vacancies arise. In 

 many instances particulars are given in the list as to the 

 .\cts of Parliament under which appointments are made, 

 and the regulations and conditions governing the selection 

 of candidates for them. Intended primarily for the use of 

 professional chemists, the publication should be found 

 useful by authorities and persons interested in the applica- 

 tions of chemistry to purposes of State and in the pro- 

 motion of higher chemical instruction. 



A SECOND edition of Mr. G. M. Norman's " Systematic 

 Practical (-')rganic Chemistry " has been published by Mr. 

 W. B. Clive at the University Tutorial Press, Ltd. 

 Various alterations and additions have been made to the 

 book in order to meet the new requirements of the Board 

 of Education syllabus in the subject. 



The popular lectures to be given at the Royal A"ictoria 

 Hall, Waterloo Bridge Road, S.E., on Tuesdays during^ 

 February, include the following : — Mr. H. S. Rowell, on 

 "Aeronautics"; Mr. Horace W. Monckton, on "Berk- 

 shire, Geological, Geographical, and Historical"; and Mr. 

 E. Cuthbertson, on "The Constitution of .'\toms." 



CoTTERiLL AND Sl.4de's well-known text-book, " Lessons 

 in .Applied Mechanics," has now been published by Messrs. 

 Macmillan and Co., Ltd., in two parts. The first volume 

 includes the sections dealing with the principle of work 

 and hydraulics, and the second those concerned with the 

 strength of materials and structures. The separate volumes 

 meet the needs of students preparing for the various 

 examinations in applied mechanics held by the Board of 

 Education. 



