>64 



NATURE 



[Februakv 14, 1895 



closely his arguments ; but that they are worthy of the 

 deepest attention, will be realised by all arachnologists 

 who are acquainted with M. Wagner's previous works. 



Perhaps the highest praise that can be bestowed upon 

 this work, is to say that, even when stripped of its 

 theories, it quite reaches the high standard of excellence 

 attained by M. Wagner's previous papers, and that the 

 great value of the theoretical part lies in the fact that 



the key to all problems is sought in the hypothesis of 

 evolution by means of Natural Selection. 



The memoir is admirably illustrated with ten litho- 

 graphed plates, of which eight are coloured, and, in 

 addition, with two hundred and fifty-two diagrams in the 

 text. The figure we here select for reproduction, to give 

 an indication of the nature of the rest, represents the 

 female of Ocyale mirabilis carrying her cocoon. 



R. 1. 1'. 

 EUmentarY Practical Chemistry, Inorganic and Orj^anic. 



ByJ. T. Hewitt, M.A., D.Sc, Ph.D., F.C.S., and F. 



G. Pope. Pp. 4;. (London : Whittaker and Co.) 

 .\l.THOLGH the authors of this small book have confined 

 themselves to such parts of elementary c|ualitalive 

 analysis as find a place in .Stage I. of the Science and 

 .■\rt Department Syllabus, neither in general plan nor 

 in details of treatment does the book possess any 

 educational advantage over its many competitors. A 

 mere recital of reactions cannot be considered as 

 " Elementary Practical Chemistry." Surely it is possible 

 to present even the array of facts utilised in analysis in 

 such a manner as to comply with the fundamental re- 

 quirements necessary to be fulfilled by all educational 

 works designed for young students of science. The pro- 1 

 duction of compilations of the present type will probably 

 cease to exist when the new regulations for Organised 

 Science Schools come into force. We may then, perhaps, 

 look for the production of really philosophical text-books 

 arranged on sound educational lines, and yet calculated 

 to minimise the very real difficulties encountered by the 

 beginner. Putting aside these fundamental considera- 

 tions, it is only just to say that the authors have brought 

 together a strictly limited set of reactions with lew 

 positive inaccuracies. 



How to Live in Tropical Africa. ByJ. Murray, M.D. 



Pp. 252. (London : George Philip and Son, 1895.) 

 So far as literary merit is concerned, this is a poor book. 

 The text is disjointed, it is too full of unnecessary 

 quotations, and there is too much tautology. liut if only 

 the subject-matter is considered, the verdict is that the 

 book is a trustworthy guide to tropical hygiene, and a 

 useful manual on the cause, prevention, and cure of 

 malarial fevers. The importance of such a handy volume 

 to emigrants and visitors to Africa can hardly be over- 

 stated. And as the book is the outcome of medical 

 experience, it possesses exceptional value. 

 VO I 3 JO, VOL. 5 I ] 



LETTERS TO THE EDITOR. 



[ The Editor docs not hoi J himstlf rtsponsibU for opinions t.\- 

 pressed ty his corresponJenls. Ntilher can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. ] 



The Liquefaction of Gases. 



Prof. Olszewski's letter in Nature of January 10 is a more 

 seiipus mailer ihan a claim for pricrily. The letier ch.-»rges 

 Pm(. Dewar wiih allowing the impresMon to go abroad that he 

 has carried out much original research into the methods of 

 liquefying ihe more permanent gases, and the properties of the 

 liquids produced ; whereas, according lo Prof. Olszewski, most 

 of Prof. Dewar's experiments have been merely repetitions of 

 work ('one by others. 



In his brief coir.iminicalion lo Nature (January 10), Prof. 

 Dewar has been too modest either to defend himself or to meet 

 his opponeni. Forlunaiely, he makes one definiie statement : — 

 'A reference to ihe /Viheedi n^s of ihe Royal Institulion 

 between the years 187S and 1893 will be sufficient to remove 

 the suegestion thai the apparatus I use has been copied from 

 the Cracovie HuUelin of 1890. " 



I have followed Prof. Dewar's recommendation, and mace 

 references to \):\e Prcceediiij^s o\ the Royal Insiituiion. In his 

 lecture at Ihe Ro>al Institulion onjunc 13, 18S4 (Proc. A". /., 

 xi. 14S), Prof. Dewar relers to Me-srs. Ol-zewski and 

 Wroblewski as having " recently made such a spk-ndid success 

 in ihe produciion and maintenance of low temperaiure." He 

 desciibes and figures an apparatus which is asligtitly modilied 

 form of that o( the Polish professors, which in turn was derived 

 from the api aratus of Caillelel ; and he says: "Provided a 

 supply ol liquid ethylene can be had, there is no difficulty in 

 repealing all ihe experiments nf the Russian observers. ' No 

 claim is made here to originality in the essentials of the 

 apparatus, ror in the expeiinients performed. The 

 apparatus referred lo by Prof. Llewar in his It dure 

 ol June, 1S84, was used by Prol. Olszewski in 1SS3, 

 and was improved by him in 1^84; in 18S7 the ap- 

 paralui- was made capable ol liquefying ONygen and other g.ises 

 in coni-idcial'le quaniiiies at the ordinary atmospheric pressure 

 (see Olszewski, I'hi!. Mag. February 1895, 189-190). In 1S90 

 ihe apparatus was so improved that from joto loocc. of liquid 

 ox>gtn could be produied by it (see Olszewski, Phil. Mag. 

 February 1895. 192-193). Pri f. Ol.szewski siaies (Nature, 

 January 10) thai a description of this improved ap| .-xralus was 

 sent 10 Piol. Dewar. A year after this, on June 26, 1891, 

 Prof. Dewar delivered a discourse on Faraday's work at the 

 Rojal Institution. The published al siract of this lecture (/"/w. 

 K. J. xiii. 481) contains a phoiograph of the pumps and engines 

 j used in ihe laloiatoiy ol the Royal Institution, and a photo 

 graph of the arrangement of ihe apparatus on the lecture table ; 

 bill it is impossible to make out the details of the apparatus 

 liom these pholoj;raphs. So far as can be judged from the 

 Proceedings of the Royal Institution, Prof. Dewar did not show 

 larne quanlitics of liquid oxjgcn, nitrogen, cr air in his 

 lectures until June 10, 1892, when be placed before his audience 

 a pint of liquid oxygen. Two years before ihis Prof. Olszewski 

 had obtained 100 c.c. of liquid oxygen, and he tells us in his 

 letter to Naiuke (lanuary io)ihai 200 c.c. of this liquid were 

 prepared and exhibited by him in July 1891. A pint is 1111- 

 doubicdly more than 2coc.c., but unless one does something 

 wilh the larger qunnlity wlii.h cannot be done equally well with 

 the smaller, nothing is ganed by conducting ihe manufacture 

 on the large scale. 



I can find no other mention of the apparatus used at the 

 Ro)al Institution for liquefying large quaniitiesof gases. There 

 is indeed no accurate ilescription in the Proceedings ol that 

 Institulion of the apparatus used by Prof. Dewar. if Prof. 

 Dewar has made markcil impiovcmenls in any essential parts 

 o( Prof. Olszewski's apparatus, why has he not pulilished an 

 accurate description of these impiovemtnis in some recognised 

 scieniific journal ? 



A relerence lo the Proceedings of the Royal Institution is 

 Ihm sufficient, not loreniove, bui 10 strengthen, " the suggestion 

 that the apparaius I [Prof. D<wai] use, has been copied Ironi 

 lie Cractvie liullelm ol 1890," or ai least ihat it has been 

 hniri'tted from detciiptions of apparatus devised by Prof. 

 Olizwli. 



