3Su 



XA TURE 



[August 27, 1908 



face of a drum intervals of one-hundredth part of a 

 second. He claims to obtain almost absolute 

 uniformity of motion for a sufficient length of run, and 

 accurate records of the corresponding tractive force 

 and velocity of advance during the part of the run 

 when uniform motion occurs. The system is said to 

 have been adopted by the German Admiralty, and in 

 some of the technical institutions of Germany. Its 

 operation and results will be watched with interest ; 

 but in the opinion of the writer the new method is 

 not likely to supplant the Froude system, although 

 it may come into use as a supplementary method of 

 making rapid and fairly accurate " first approxima- 

 tions " to resistance. Even minute errors are magni- 

 fied so greatly in passing from a model to a full- 

 sized ship or propeller that the nearest possible ap- 

 proach to accuracy in the model experiments must be 

 obtained, and this may justify a continuance of the 

 greater expenditure on the experimental tanks and 

 apparatus involved in the Froude system. Experience 

 will decide this matter, and an extended comparison 

 of results obtained on the old system and the new 

 with models of identical form should afford conclu- 

 sive evidence as to the best course to be followed in 

 future. Experiment alone can be trusted, as no theo- 

 retical investigation or mathematical formulas can deal 

 adequately with the complex conditions of ship- 

 propulsion. 



Scientific analysis of the results obtained from 

 systematic series of experiments on the forms of ships 

 and propellers will certainly e.\ercise great influence, 

 and enable designers to proceed with greater cer- 

 tainty in future. There are already many examples 

 of what may be hoped for ultimately in the published 

 papers of Mr. R. E. Froude, Mr. Taylor and others. 

 At present the volume of such information is in- 

 sufficient, and many departments of knowledge re- 

 main obscure. As to methods of analysis, little can 

 or need be said at present ; when materials are 

 available suitable methods will be devised. An in- 

 teresting attempt to deal with the matter in the light 

 of present knowledge will be found in a paper read 

 before the Institution of Naval Architects by Captain 

 Hovgaard, now professor of naval architecture in 

 the Massachusetts Institute of Technology, and re- 

 sponsible for the training of the naval constructors 

 of the United States Navy. Like Mr. Taylor, Captain 

 Hovgaard owes his professional training to the Royal 

 Naval College, Greenwich, and does honour to that 

 institution. His " Analysis of the Resistance of 

 Ships " is worthy of close study, and is based on 

 wide knowledge of the subject. But his conclusion 

 will commend itself to ever}' student. " Not until 

 tanks are established for research work .... will 

 questions like the present one and many others 

 equally important find their solution." Much may 

 be looked for from the tank at Bushy which Mr. 

 Yarrow has offered to establish, provided shipbuilders, 

 marine engineers and shipowners will guarantee the 

 costof its maintenance. Such an offer cannet fail to be 

 accepted, and the sooner the work of constructing 

 the tank is begun the better will it be for British 

 shipping. W. H. White. 



NO. 2026, VOL. 78] 



LECTURES ON EVOLUTION. 

 Vorlcsitiigen iiber Deszendenztheorien mil besondercr 

 Beriicksichtiguijg der botanischen Seite der Fragc. 

 By Prof. J. P. Lotsy. Pp. vi-t-sSi-rgg. Theil ii. 

 (Jena : Gustav Fischer, 1908.) Price 12 marks. 



THE second part of Prof. Lotsy 's book contains the 

 substance of twenty-eight lectures, completing 

 his course on evolution. Though making no claim 

 to have broken new ground, the work is of real use. 

 The presentation of contemporary knowledge of these 

 subjects which it gives is comprehensive in scope and 

 accurate in treatment. The author does not suffer 

 from the delusion that in evolutionary science finality 

 was reached fifty years ago, and it is a pleasure to 

 see the results of modern research incorporated with- 

 out ludicrous mistakes. This is probably the best 

 text-book of the subject yet compiled. . 



There are occasional signs of vacillation between 

 the old and the new conceptions. For example, as 

 an instance of a dissimilarity between reciprocal 

 crosses. Prof. Lotsy brings forward Bilbergia nutans 

 X vittata on evidence which would have satisfied the 

 older observers. Knowing the sources of ambiguity 

 which affect such evidence, he remarks that nossibly 

 the dissimilaritv may nevertheless be due merely to 

 " Pleiotypie in F,." Rather, until it shall have been 

 ascertained by repeated experiment that there is con- 

 sistent dissimilarity between the reciprocals, the pre- 

 sumption is strong that the differences observed are 

 an expression of heterogeneity in the cross-bred 

 generation as such, and are not dependent on the 

 parental roles allotted to the respective species. The 

 break with tradition which Mendelian discovery has 

 made is, indeed, so wide that a generation must pass 

 before the older interpretations disappear, and evolu- 

 tionists come to think easily and habitually in terms 

 of the new system. This book will do a good deal 

 towards accelerating the change. 



To professed students of genetics this text-book 

 may be recommended as bringing a quantity of fresh 

 materials under consideration which have not pre- 

 viously been dealt with in a consecutive treatise. 

 Of these materials some are ancient and some modern. 

 For the first time, probably, Gartner's work is pre- 

 sented in summary, and though, judged by modern 

 standards, his experiments are fragmentary and im- 

 perfect, many readers will thus become aware of the 

 range of observation which they covered. In another 

 useful chapter a clear abstract of Nageli's views is 

 provided. Prominence is given to the remarkable ex- 

 periments of Klebs on Setnperviviiin Funkii showing 

 the influence of external conditions. Facts of this 

 class are extraordinarily difficult to interpret, and until 

 exhaustive work has been done on the same lines 

 we must perhaps abstain from confident interpretation 

 altogether. As a subject for genetic research the 

 Sempervivums are most attracti\e. To turn over 

 Jordan's plates of this polymorphic genus in the 

 " Conspectus " — still more to see his actual collection 

 of living plants now preserved in Miss Willmott's 

 garden — is to realise the great possibilities which the 

 material provides. It is to be hoped that someone 

 will devote himself in good earnest to an analysis of 

 those protean forms. 



