Nov. 1 8, 1886] 



NA TURE 



5t 



living zooids of this remarkable group of Hydroids. It 

 \vas M. nodosa, occurring at Tahiti, that afforded Prof. 

 Moseley the material for his brilliant confirmation of the 

 observations of L. Agassiz. Twelve plates, the figures 

 on which are beautifully executed by Mr. H. Gawan, 

 accompany this Report. 



The concluding Report in this volume is by Prof. Sir 

 William Turner, being on the Human Crania, &c., 

 collected during the cruise. This forms Part 2, being on 

 the bones of the skeleton, and is an Essay on the Com- 

 parative Osteology of those Races of Men whose bones 

 are described in the Report, for it incorporates the study 

 not only of the material collected during the cruise of the 

 Challenger, but that brought together by the authors' 

 eminent predecessors in the Chair of Anatomy in the 

 University of Edinburgh. 



Just a century ago Camper pointed out some of the 

 differences existing between the pelvis of a Negro and a 

 European, and since then a vast amount of information 

 on the subject has been accumulated, and so far as the 

 races described in this Report are concerned, it has been 

 exhaustively treated by Sir W. Turner. He classifies the 

 pelvis into three groups: dolichopellic, with a brim index 

 above 93 ; mesatipellic, with a brim index from 90 to 95 ; 

 and platypellic, with index below 90. As to the race and 

 age characters of the pelvis, the details, however inter- 

 esting, are too technical to be abstracted. In reference 

 to the question of how far the mode of life may act as 

 modifying the transverse diameter of the pelvic brim, 

 we may add that the expression " to sit on one's 

 hunkers," would be readily understood in the North of 

 Ireland, where it is an attitude strictly forbidden to young 

 people. In the section treating of the spinal column, 

 the subjects of peculiarities of individual vertebras and the 

 lumbar curve are investigated ; and in another section 

 the scapula, inferior and superior extremities, are exa- 

 mined. In a concluding section we have a general sum- 

 mary, and an appendix to the first part of the memoir on 

 the " Human Crania," in which some additional details 

 are given of some crania from Australia, the Sandwich 

 Islands, New Guinea, and Fuegia. An index to both 

 parts also accompanies this Report, which is illustrated 

 by three plates of the pelves of difterent races. 



The greater portion of the manuscript of these two 

 large volumes was handed to the editor between July 

 1885 and July l8S6, and the editor is to be congratulated 

 on the successful manner in which this immense amount 

 of scientific matter has been seen through the press. 



ELEMENTARY DYNAMICS 

 Lessorh in Elementary Dynamics. Arranged by H. G. 

 Madan, M.A., Assistant Master in Eton College. 

 Pp. 180. (Edinburgh : W. and R. Chambers, 1886.) 



IN this little book the author has provided teachers of 

 elementary mechanics with a rich storehouse of ma- 

 terials for experimental demonstrations, although the 

 work is not quite satisfactory in some other respects. 

 His endeavour has been to explain some of the pro- 

 perties of matter, Newton's laws of motion, and the 

 modern conceptions of energy and work, in such a manner 

 as involves only the most elementary knowledge of 

 mathematics. Thus symbolical reasoning and formula? 



are dispensed with, and nothing assumed beyond a 

 knowledge of arithmetic and a little easy geometry. 

 There is a successful attempt made to arouse a real 

 interest in the subject by continual reference to pheno- 

 mena of every-day life, and especially by illustrations 

 drawn from the 'sports and games of the pupils. 

 In some cases detailed instructions are given for per- 

 forming the experiments. These are valuable, and 

 similar aid might with advantage be provided in many 

 other instances. 



The author is of opinion that mechanics ought to have 

 the first place in a boy's scientific education. This posi- 

 tion would be strengthened, if some series of simple ex- 

 periments, to be performed by the pupils themselves, were 

 provided, and regarded as essential. 



Some expressions, such as "above," "below," "on 

 the same level," which are usually left undefined, have 

 their exact scientific meaning pointed out. On the 

 other hand, there is occasionally looseness and con- 

 fusion in the use of technical terms. For example, in 

 Section 103 we read : " Momentum is the term used to 

 express the force with which anything is moving." In 

 Section 159 we have the accurate statement that, by find- 

 ing the momentum of a body, we learn what impulse has 

 been applied to it : here the accepted expression for the 

 time-integral of a force is used, but we do not notice any 

 definition of the word "impulse"; and the exposition of 

 the second law of motion appears vague in consequence. 

 Similarly, Xkm force exerted in throwing a cricket-ball is 

 spoken of in Section 156, where the time-integral of the 

 force is in question. 



Section 302 is devoted to the " exact valuation of the 

 energy in a moving body," and the usual expression — 

 energy = 2 (mass X velocity'-) — is obtained, but by a pro- 

 cess which is at least startling. Witness these state- 

 ments : — " If the work could be done in an instant, the 

 energy would be exactly expressed by the product of the 

 mass X velocity" ; " and again, " The whole amount of 

 work which a moving body can do in the time during 

 which its motion is being stopped will correspond to the 

 average or mean amount of energy between that which it 

 has at the beginning of the time and that which it has at 

 the end of the time." Uiide, quo veni ? 



After the preceding, it is a small matter to refer to 

 Section 311, where this statement occurs : " The motion 

 of the pendulum is an accelerated motion, and, as in al 

 other uniformly accelerated motions, the spaces de- 

 scribed are as the squares of the times." Here, of course 

 the reasoning is fallacious ; and, although the proof 

 intended is sound, it involves the doctrine of limits, and 

 wants development. It is surely better at this stage 

 of the pupil's progress to rely on the experiments in 

 Section 312. 



There is an appendix on the metric system, and, in 

 conclusion, a dozen pages of questions and exercises on 

 the several chapters of the book. A. R. W. 



OUR BOOK SHELF 



Food-Grains of India. By A. H. Church, M.A. (Lon- 

 don: Chapman and Hall, 1886.) 

 A WELL-WRITTEN, well-illustrated, and well-turned-out 

 volume. Its thinness only enhances its elegance. Its 

 illustrations, by Mr. G. W. Ruffles, are charming, clear. 



