54 



NA TURE 



[May 1 6, 190; 



Before dealing with the special form of turbine 

 most suitable for marine purposes, the author gives 

 a condensed and useful account of the development 

 of the turbine from the time of Hero to the present 

 day. In the second chapter the main features in the 

 design of marine turbines are discussed, and then a 

 detailed account is given of the method of blading 

 the turbine drum and casing. In a convenient table 

 at the end of this chapter the author gives in detail 

 the sizes of the blades and their spacin.g for the 

 H.P., L.P., and astern turbines of an ocean li-ner. 

 The next chapter is well illustrated, and the repro- 

 ductions of photographs, taken at various stages in 

 the process of building a large set of marine turbines, 

 will do much to make the non-technical reader 

 familiar with the more important details in turbine 

 construction. The thermodynamic principles which 

 govern the design of turbines are then brieflv touched 

 upon, and their application illustrated bv the calcu- 

 lations, necessary in determining blade dimensions 

 for a channel steamer, being fully worked out. The 

 success of the marine turbine is so entirelv depen- 

 dent on the efficiency of the propeller to which it is 

 connected that it was most desirable that Prof. Biles 

 should in these lectures discuss fully the theory and 

 design oi the screw propeller as employed in turbine 

 vessels ; the important and complete series of experi- 

 ments carried out at the United States Navy Tank 

 at Washington are admirably summarised ; the 

 results are illustrated by graphs, and their applica- 

 tion to the design of a •jsropeller which has to work 

 under any given set of conditions is clearly 

 e.\plained. 



The book concludes with a summary of all the 

 trustworthy information at present available as to 

 the comparative economy of turbine and reciprocating 

 marine engines, and it is worth pointing out that, 

 judging from the performances of certain cross- 

 channel steamers, the considerable economv of the 

 turbine-engined steamer which is shown during the 

 preliminary trials is apparentlv not maintained in 

 active service, though the author has every confidence 

 that this loss in economy, which he considers is due 

 to cavitation, will eventually be overcome. 



T. H. B. 



A First Year's Course in Geometry and Physics. By 

 Ernest Young. Parts i. and ii. Pp. ' viii + loi'. 

 (London : George Bell and Sons, 1907.) Price 

 IS. 6d. 



This satisfactory first year's course of work in geo- 

 metry and physics recognises fullv the desirability 

 of making the introductory lesson's in mathematics 

 and science as practical as possible. The author is 

 an experienced schoolmaster who understands the 

 need of setting young pupils to do things for them- 

 selves if they are really to understand the subjects 

 under consideration. Though there is little that is 

 novel in the methods adopted, the book provides an 

 abundance of well graduated exercises suitable for 

 boys of twelve to thirteen years old. 



New Geometry Papers. By Rupert Deakin. Pp. 

 lo;?. (London : M.icmillan and Co., Ltd., iqo;.) 

 Price IX. 



The recent changes in teaching geometry have 

 rendered Mr. Deakin's "Rider Papers on Euclid" 

 of little use in most schcmls, and the present book 

 is intended to serve a similar purpose under the new 

 conditions. The papers are graduated and arranged 

 in order of difficulty, while hints are provided on the 

 method of solving riders. The collection should prove 

 useful as a supplement to the school text-book of 

 geometry. 



NO. 1959 VOL. 76] 



LETTERS TO THE EDITOR. 



[The Editor docs not ludd himself responsible for opinions 

 expressed by his correspondents. Neither 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 Name of the Cave Horse. 



In the paper on the derivation of the horse in the April 

 number of the Quarterly Review, to which reference was 

 recently made in Natlre, Prof. J. C. Kwart expresses 

 the opinion that the wild Mongolian horse, commonly 

 known as Przewalski's horse, is identical with the horse 

 depicted by the prihistoric inhabitants of La Madelaine 

 Cave, in the Dordogne. The same view is even more 

 emphatically expressed by Dr. E. L. Trouessart in the 

 Bulletin of the Paris .Museum (igol), p. 453). No mention 

 is made by either writer of any change in nomenclature 

 involved in this identification. 



In the Phil. Trans, for 1906 .Sir R. Owen described 

 the prehistoric horse of the cavern of Bruniquel (Tarn et 

 fiaronnr) as Equiis spehwiis ; and although he estimated 

 the hi^ight of the animal at 13J hands, it is practically 

 certain that it was rially much less, as he was not aware 

 of the relatively large size of the molars in the Mongolian 

 horse. 



Now it can scarcely be doubted that the small pre- 

 historic horse of the Bruniquel cave is identical with the 

 one depicted by the prehistoric hunters of La Madelaine, 

 and as there is equally little doubt that both are merely 

 races of Equiis cuhallKS, the name of the La Madelaine 

 horse is Equiis eaballus spelaeus. 



Hence, if Messrs. Ewart and Trouessart are right, it 

 is also the title of the wild Mongolian horse, the name, 

 Eqiius przewalskii dating only from 1881. It is true that 

 there is a possibility that a name given by Hamilton 

 Smith to a horse supposed to be from Tatary may ante- 

 date both spelaeus and przewalskii, while Eqiius fossilis, 

 dating from 1836 or 1846, may possibly be identical with 

 spelaeus. Nothing certain can, however, be affirmed with 

 regard to either of these points. 



The name E. c. spelaeus for the La Madelaine horse 

 certainly cannot be ignored, but it seems inadvisable that it 

 should be made to supersede E. c. przc-Malskii, esrerially 

 when the wide separation in time and space between the 

 types of the two is taken into consideration. A way out 

 of the difficulty may be found in a refusal to admit Messrs. 

 Ewart and Trouessart's absolute identification of the fossil 

 with the living form, and to regard them as distinct, 

 although closely related, races, when they will stand re- 

 spectively as Equus eaballus spelaeus and Equus eaballus 

 przewalskii. 



I may add that I cannot agree with Prof. Ewart in 

 regarding the skull of Przewalski's horse as conforming 

 to the type in which the face is bent down on the cranial 

 axis. On the contrary, it is more or less of the straight 

 tvpe, in common with the prehistoric horses of Europe. 

 The bent type seems to me characteristic of domesticated 

 breeds, especiallv thorouEjhbreds and .\rabs, and as it also 

 occurs in the fossil Indian Equus sivalensis, my sugges- 

 tion that .^rabs and thoroughbreds are descended from 

 that species, while the ordinary " cold-blooded " European 

 horses trace their origin to the " Przewalski," is strongly 

 confirmed. In a short time I hope to put skulls of the 

 two types on exhibition in the Natural History Museum, 

 so that visitors can judge for themselves on the point at 

 issue. R. LVDEKKKR. 



The Enigma of Life. 



In the review of my book " The Evolution of Life " in 

 Nati're of May 2 (p. i). "J. .■\. T." admits his inability 

 to " point out precisely where my experiments are 

 fallacious," and says he does "not know what to answer 

 imless it be that the sterilisation was inadequate, or that 

 the preparations were contaminated before the photo- 

 graphs were taken." But the adequacy of the sterilisation, 

 in accordance with all existing knowledge, is fully shown 

 in the book : and, as for the last suggestion, it seems 



