May 19, 1904] 



NA TURE 



53 



cargo steamers in the most rapid and efficient manner 

 possible. 



iMr. Cunningham has therefore had unrivalled 

 opportunities of acquiring both a theoretical and 

 practical knowledge of dock construction, and in the 

 volume now under notice he has brought together in 

 a concise and well organised form the results of the 

 knowledge thus acquired. The author has not, how- 

 ever, relied solely on his own experience, but has freely 

 made use of the information contained in the 

 numerous papers on dock matters contributed to the 

 Proceedings of the Institution of Civil Engineers and 

 to the numerous reports of the International Navi- 

 gation Congresses and other technical societies. Of 

 these he has evidently been a diligent reader, as few 

 points of interest in the Proceedings of the societies 

 or in the technical journals that have been dealt with 

 during the last few years seem to have escaped his 

 notice. 



While the study of this book may be regarded as 

 essential to the younger engineers engaged in dock 

 work, it will be invaluable as a book of reference to 

 the e.\pert engaged in this branch of engineering and 

 its cognate interests. 



The book is divided into twelve chapters, dealing in 

 an exhaustive m;mner with the designing and con- 

 struction of docks, the materials and plant required, 

 the thcorv of construction of the walls and gates, the 

 equipment and working of docks when constructed, 

 the appliances required for the handling and transport 

 of cargoes to and from the docks, and for repairing the 

 vessels. The book is well illustrated, there being no 

 less than 34 folding plates and 468 illustrations in the 

 te.xt. The book does great credit both to the author 

 and to the publisher, but, of course, the greatest merit 

 belongs to the former for having furnished the dock 

 engineer with such a valuable aid to his work. 



Electric Lightini; and Power Distribution. Vol. ii. 



By \V. P. Maycock, M.l.E.E. Pp. xxii + 684. 



(London : Whittaker and Co., 1903.) Price 75. 6d. 

 This little book covers a very great deal of ground, 

 so that it is hardly necessary to say that no subject is 

 discussed in any great detail. The opening chapters 

 deal with dynamos, alternating currents and alter- 

 nators, and these are followed by a chapter on 

 electricity meters, in which most of the leading tvpes 

 are described and illustrated. The next chapter deals 

 with motors; a dozen pages in this chapter are all 

 that are devoted to electric tramwavs and railways, 

 which will give some idea of the amount of consider- 

 ation which each branch receives. Other chapters 

 deal with batteries, transformers, and generating 

 stations. The treatment throughout is of a very 

 elementary character, but the descriptions are clear and 

 concise, and the illustrations well selected and very 

 clearly reproduced, so that the book should be of service 

 to the student for the City Guilds and similar techno- 

 logical examinations, for whom it is primarily in- 

 tended. 



Builders' Quantities. By Herbert C. Grubb. Pp. 



viii + 227. (London: Methuen and Co., 1904.) 



Price 45. 6d. 

 This book has been prepared more particularly for the 

 use of candidates studying for the examination in 

 builders' quantities held by the City and Guilds of 

 London Institute. The modes of measurement and 

 examples of " taking off " are given in order for the 

 work of all the trades employed in the erection and 

 completion of a building ; and these sections are 

 followed by explanations of squaring dimensions, 

 abstracting, and billing. The text is illustrated bv 

 seven t\-seven figures. 



NO. 1 5^03, VOL. 70J 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertalie 

 to return, or to correspond with the xvrilers of. rejected 

 manuscripts intended for this or any other part of Naturk 

 Ho notice is taken of anonymous communications .] 



The Origin of the Horse. 



The receipt of a copy of Prof. J. C. E wart's admirable 

 paper on " The Multiple Origin of Horses and Ponies " 

 suggests a few remarks. The paper in question is from the 

 Transactions of the Highland and .Agricultural Society of 

 Scotland, 1904 — one could wish that it had appeared in a 

 publication which comes more regularly under the notice of 

 zoologists. In a previous paper (Proc. Roy. Soc. Edin- 

 burgh, 1903) Prof. Ewart had shown conclusively that Equus 

 prjevalskii was not a hybrid between the kiang and the 

 common horse, and had arrived at the conclusion that it 

 might very well rank as a valid species. Lydekker in 1902 

 had proposed to regard E. prjevalskii (or prseivalskii) as 

 a subspecies of E. caballus, and now. Prof. Ewart does the 

 same, while recognising also two other subspecies, 

 E. c. typicus and E. c. celticus. The animal named typicus 

 is the Norse horse, which is arbitrarily selected as the type 

 of the Linnean caballus. The Celtic pony, still surviving 

 in the pure state in Iceland, is given the new name 

 E. c. celticus. In its way, Prof. Ewart 's demonstration of 

 the distinctive characters of this animal deserves to rank 

 with Darwin's treatise on the primrose, as an example of 

 genius applied to common things. The case is so clear that 

 the author himself is evidently half inclined to regard the 

 Celtic pony as a valid species, and it seems to me that the 

 facts justify us in recognising three species of living horses, 

 E. prjevalskii (Poliakoff), E. celticus (Ewart) and E. 

 caballus (L.). The indications are that these animals were 

 quite distinct in the wild state, and the fact that various 

 blends between caballus and celticus exist in domestication 

 is no more proof of specific identity than the same sort of 

 thing is among the dogs, which nobody doubts to have 

 originated from more than one wild species. 



The use Prof. Ewart makes of the prehistoric cave draw- 

 ings of horses is most suggestive. Possibly these sketches 

 may have been taken a little too seriously in some instances, 

 too little allowance being made for eccentricities in draw- 

 ing. Fig. 27, from the Kesserloch cave, has a remarkably 

 long body, and one might joyfully recognise the Equus 

 scotti. Gidley, were it not that that animal inhabited the 

 plains of Texas and New Mexico.' Prof. Ewart accepts 

 the opinion that the living American horses are wholly of 

 Transatlantic origin. While this is probably correct, I was 

 surprised on looking into the matter a few years ago to 

 find that the evidence was not so complete as I had sup- 

 posed. It is said that the natives showed great surprise 

 at the horses of the Spaniards, being evidently unacquainted 

 with the animals. This was to be expected, for if wild 

 horses lived in .America at the time of Columbus, thev 

 surely were not in the " tierra caliente," but rather to the 



1 The New Mexico record is based on a molar toolh found by Miss Ada 

 Springer in the Pleibtocene beds of the Arroyo Pecos, Las Vegas, and ex- 

 amined by the writer. It differed in no respect from Gidley's description 

 and figure. Mr. Gidley kindly m.ide for me a number of skull-measure- 

 ments from the types of £"- .Jtrtj///, and I found upon comparisons that the 

 five specimens were much more uniform than a similar series of E. cabaVaiS 

 picked at random would be. This may be attributed no doubt to the 

 greater uniformity of the wild species, but also to these particular specimens 

 being apparently (from the circumstances of their discovery) members of the 

 same herd. The skulls were 571 to sgo mm. long, and differed from any 

 caballus o{v!\\\cSi I had measurements in (i) the rather longer muzzle, with the 

 upper dental series (molars and premolars) considerably longer, 195 to 

 J04 mm., and (2) apparently in the greater breadth between the orbits 

 above, but Mr. Gidley afterwards wrote that he found that while the 

 breadth between the anterior borders of the orbits of iiotti is slightly 

 greater than in large skulls of caballus, the breadth between the fosterhr 

 borders is less ; hence it would seem that the eyes of scotti looked less for- 

 ward than those o{ caballus. The other measurements ; — zygomatic breadth, 

 greatest breadth of muzzle, least breadth of palate, distance between molars 

 of opposite sides, and the greatest breadth of posterior nares, all fall wiihin 

 the limits of variation of £". caballus. Hence it is apparent that E. scotti 

 was in many respects similar to cabaUus, as Mr. Gidley indicated in hi.s 

 paper on the subject. The bones other than the skull, taken separately, 

 could not be distinguished from those o! caballus. Other differences in the 

 skulls than those mentioned have been fully described and illustrated by Mr. 

 Gidley, and the facts need not be repeated. No doubt a more minute siudy 

 of the osteological characters of fossil hois..-s would throw valuable light on 

 the significance of variations in the living forms. 



