2l8 



NA TURE 



[July 9, 1908 



western Asia before it followed the big game into 

 Africa (the last refuge of the latter before the advanc- 

 ing power of Neolithic man). But if protection from, 

 cold and wet be the inducement which led to the 

 development of a mane in the male lion, how about 

 the lioness? The more probable explanation is that 

 the mane of the lion arose both as a male ornament 

 and as a protection for the throat and chest in sexual 

 combats with other males. Mr. Selous comments on 

 the distincth- spotted limbs possessed by some adult 

 lions and lionesses ; he quotes the special name given 

 to this type by Boer hunters. He will have been in- 

 terested in the paper by Mr. R. I. Pocock in the 

 Annals and Magazine of Natural History (November, 

 1907) on the significance of the pattern — the rosettes, 

 spots and stripes— of the cubs of lions (and of pumas). 



The author's notes on the fluctuations of the abund- 

 ance and distribution of the tsetse fly and its corre- 

 lation with the abundance or scarcity of the buffalo 

 are important aontributions to a subject of great 

 economic importance. His remarkable sporting ad- 

 ventures are the more thrilling because of their ob- 

 vious truth, and the quiet style of narration. 



The last chapter in the book is as valuable as any 

 in a work which is interesting from beginning to end. 

 It is devoted to the Bushmen of South .\frica— more 

 especially the Masarwa dwelling on the verge of the 

 Bechuana countries. 



Mr. Caldwell's drawings are admirable (especially 

 the study of galloping gemsbuck). Very interesting 

 are the photographs and description contributed by 

 an American sportsman, Mr. Max Fleischmann, of a 

 rhinoceros being dragged under water (pre>umnblv) 

 by crocodiles. 



H. H. JOIINSTO.V. 



'WATER POWER. 

 Hydraulics and its Applications. By A. H. Gibson. 

 Pp. xvi + 757; with diagrams and illustrations. 

 (London : Archibald Constable and Co., Ltd., 1908.) 

 Price 185. net. 



JN this intensely practical age, science is chieflv 

 exploited for utilitarian ends. The fascination of 

 experimental research lies, as Cap'n Cuttle would 

 observe, "in the application thereof." We seek to 

 know, not for any mere pleasure to be derived from 

 the acquisition of knowledge, but in order to bring 

 that knowledge to bear upon everyday problems of 

 life, labour, and economy. 



There is something, therefore, particularly fitting 

 and appropriate in the title of Mr. Gibson's book, 

 "Hydraulics and its .Applications," for hydraulics is 

 an eminently practical branch of natural science. 

 Moreover, it is a science difficult to define in that it 

 has no fixed limitations. It embraces the study of all 

 questions in hydro-mechanics in which the motion of 

 water produces or is connected in any way with useful 

 work. In a very special sense it lies within the 

 province of the engineer and the manufacturer. 



On its theoretical side, hydraulics presents a number 

 of difficulties. Assumptions have to be made which 

 are not strictly justifiable in reality; yet without them 

 NO. 2019, VOL. 78] 



the solution of problems would be well-nigh imprac- 

 ticable. There is, therefore, something necessarily of 

 the nature of compromise about the subject, and Mr. 

 Gibson strikes this keynote at the outset of his work 

 by explaining that the questions of hydraulics can 

 only be discussed on the basis of the assumption that 

 water is a perfect fluid (which it is not), absolutely 

 non-viscous and inelastic, with the introduction of 

 empirical constants to bring theoretical results into 

 conformity with the records of actual observation. 



Despite, however, the very practical suggestion of 

 its title, Mr. Gibson's treatise must be set down as 

 primarily a theoretical work. It postulates a know- 

 ledge of mathematics and mathematical processes 

 which the ordinary practical man unfortunatelv rarelv 

 possesses. And while the operator, as distinct from' 

 the experimentalist, will no doubt fully appreciate the 

 useful data contained in the volume and the informa- 

 tion condensed into working formute, he will at the 

 same time be inclined to regret that Mr. Gibson has 

 not dealt a little more completelv with the practical 

 side of the subject, by describing in greater detail 

 the remarkable variety of ways in which hydraulic 

 machinery is utilised in commerce, manufactures, and 

 the arts. 



Commencing with two prefatory chapters on hydro- 

 statics and the physical properties of water, in which 

 such matters as capillarity and the laws of floating 

 bodies are briefly discussed, the author introduces his 

 main subject in chapter iii. by describing the experi- 

 mental results obtained by Profs. Osborne Reynolds 

 and Hele-Shaw in regard to stream lina. flow. The 

 motion of fluids is then mathematically investigated 

 and its phenomena explained in relation to pipes, 

 bends, vortices,' and orifices. This leads on to the 

 laws of fluid friction and the resistance of ships, 

 whence the author reverts once more to pipe and 

 channel flow, and the various sources of loss of head 

 and velocity. Chapter x. takes up the question of 

 impact of jets and of pressure on submerged planes. 

 It is not until chapter xi. is reached that the practical 

 side of the subject comes under discussion, and then 

 the various and well-known types of water-wheel are 

 duly described and illustrated, including the Pelton 

 motor. Chapter xii. deals with turbine forms, and 

 chapter xiii. with the theory of turbine design. In 

 chapter xiv. there is an account of the hydraulic re- 

 ciprocating engine, with examples of the Brotherhood 

 and Rigg machines. Chapters xv. to xvii. are devoted 

 to pumps, including the hydraulic ram. The trans- 

 mission of energy by means of pressure mains forms 

 the subject of chapter xviii., while the final chapter 

 contains a brief review of a number of important 

 appliances : lifts, hoists, jacks, cranes, and jiggers. 

 It is this latter portion of the book — the manipulative 

 aspect of hydraulics — that one would have liked to 

 see expanded, even, if necessary, at the expense of 

 some of the earlier mathematical matter. The com- 

 merce of Great Britain is essentially maritime, and 

 a very large proportion of port and harbour machinery 

 is hydraulic. Dock gates, sluice penstocks, capstans, 

 coal elevators and tips are worked in the great 

 majority of cases by hydraulic power, and despite their 



