442 



NATURE 



[Februar\ 



Ehrmann's theory, that the material which ii con- 

 verted into melanotic plj^ment springs froni the blood, 

 being, indeed, haemojjlol)in which is converted into 

 melanotic pigment by the vital processes of the melanti- 

 blasts; and that the pigment is transferred by proto- 

 plasmic flow along protoplasmic threads. On the 

 other hand, Meirowsky contends that the epidermal 

 cells themselves can produce pigment, especially under 

 the influence of light, and that the ha;moglobin and 

 migrator}' melanoblast theory has been completely 

 exploded. Neither microscopic nor biochemical in- 

 vestigation has led to any decisive conclusion on this 

 c|uestion. Both sides of the controversy are fairly and 

 fully stated in this part of the monograph. 



The remaining chapters deal with leucoderma and 

 partial albinism. leucoderma is defined as an 

 acquired disease characterised by the presence of pro- 

 j*ressive white patches with convex borders surrounded 

 by increased pigmentation. It is regarded, by the 

 jiuthors, as the essential pathological pigmentation 

 change wherein is seen albinism in the making, and 

 from this point of view its study is of great import- 

 ance. Interesting suggestions as to the cause of 

 leucoderma have been made by Beigel, who maintains 

 that it is largely due to modified nerve action, pro- 

 duced by shock, illness, severe chill, or other nerve 

 upset; and by Fore!, who offers some evidence that 

 it may be sometimes due to race mixture. Many 

 excellent portraits of leucodermous subjects are con- 

 tained in the atlas. 



In the chapter on partial albinism, the nature and 

 origin of piebaldism is discussed. It is noted that in 

 some cases at least piebaldism is hereditary even as 

 to the position of spots. 



Numerous cases are cited and described of leuco- 

 •derma, piebalds, and spotlings. 



This valuable monograph will clear the ground and 

 suggest new lines of research, and the remaining 

 parts will be eagerly awaited. 



SUSPENSION BRIDGES. 

 Fonts Suspendus. By G. Leinekugel le Cocq. 

 Tome i., Fonts Suspendus Flexibles et Semi-Rigides. 

 Pp. xiv+374. Tome ii., Fonts Suspendus Rigides. 

 Pp- 330- (Paris: I. Doin et Fils, 1911.) Prke, 

 2 vols., 10 francs. 



THESE two volumes form part of the "Encyclo- 

 paedia of Science," published under the direction 

 of Dr. Toulouse, and of the subdivision dealing with 

 applied science and engineering, the general editor- 

 ship of which was entrusted to Prof. D'Ocagne, of 

 ] III ill (irv Tonts et Chauss6es. The first volume 

 ireaia of llexible and semi-rigid, and the second of 

 rigid suspension bridges. 



In the first two chapters of vol. i. the author gives 

 a brief history of suspension bridges, with short 

 accounts of some of the more famous of them, and 

 some notes on the different systems of construction 

 adopted in practice ; the rest of this volume is devoted 

 to analytical investigations of the various problems 

 A\ hich have to be solved by the designer of flexibl e and 

 semi-rigid suspension bridges. M. Leinekugel le Cocq 

 NO. 2205, VOL. 88] 



dealt first with cables employed ii ial trans 



port of minerals and other materials* atruss ravine! 

 in mountainous districts, and for similar work if 

 connection with the erection of bridges across rivers 

 where the conditions render the construction of i.' <:' 

 ing impossible, as was the case with the bridge :>' 

 the Zambezi, just below the famous falls, and .sii-i^v 

 how to determine the length and maximum stresse: 

 in such cables when the necessary data are known. 



Cables for suspension bridges are then considered 

 on pp. SS and 89 the author gives tables showing th« 

 relation between dip and span for a number of su* 

 pension bridges in Europe and .-Xmerica, and add; 

 i some notes as to the methods of constructing sue! 

 cables, and as to the physical properties of the stee 

 suitable for their manufacture. The deformations 

 produced by temperature changes and by unequa 

 loading are then fully discussed, the formulae obtaine< 

 being illustrated by the case of the Williamsburg 

 bridge and others. The effect produced by support 

 ing the cables from two piers of different height, ant 

 the design and stresses in the suspension links, ar< 

 then taken up. The next section of this volume h 

 occupied with a discussion of the methods adoptee 

 to increase the rigidity of suspension bridges and thu! 

 overcome the serious practical inconveniences whict 

 ensue when a suspension bridge is supported onlj 

 by the principal cables ; the treatment of this importani 

 problem is very thorough and complete. The firsi 

 volume concludes with some notes on the constructior 

 of the bridge platform, and on the action of the wind 

 uf>on such bridges. 



In an introduction to vol. ii., the author points oul 

 that the design of flexible and semi-rigid suspensior 

 bridges requires but little knowledge of higher applied 

 mathematics, while, on the other hand, the problems 

 encountered in the design of rigid suspension bridges 

 can only be solved by those who are well equipped 

 on the mathematical side; hence, while examples ol 

 the former class of bridge are numerous, tlie ; 

 type is only occasionally met with. The first ch 

 treats of three-hinged, rigid suspension brie: 

 general principles are first considered, both anaJ\ : 

 and graphical solutions are discussed, and full explana. 

 tions are given as to the method of determining th< 

 lengths, stresses, &c., in the bracing and struU 

 between the upper and lower members of such brit!. 

 Illustrative examples selected are the bridge at 1 

 burg over the Monongahela, and a bridge near \ ilk- 

 franche on an electric railway line in South France. 

 In the second chapter hinged bridges, with the plat- 

 form supported by oblique chains, are dealt with, tlic 

 illustrations of this class being the transporter bridges 

 at Nantes and Marseilles. The concluding chapter is 

 devoted to various important details, such as anchor- 

 ages and saddles. In the form of an apjjendix, tlie 

 author has reprinted the official regulations as tc 

 working loads, stresses, &c., in steel bridges, which 

 must be adopted when designing such structures in 

 France and other Continental countries, and also a 

 bibliography of the subject, which should prove oi 

 service to engineers engaged in this branch of bridge 

 design. T. H. B. 



