30 



NATURE 



[May 14, 1903 



quantity, and one not easiljr found practically. 

 Chapter v. is devoted to the design of masonry re- 

 taining walls; the table of thicknesses for walls and 

 the graphical solutions at the end of the chapter are 

 particularly valuable. Chapter vi. commences an im- 

 portant section dealing with transverse stress, and 

 relating mainly to the strength and stiffness of beams. 

 After discussing the position of the neutral axis and 

 the stress at a point in the section, the authors, oddly 

 enough, give a chapter on the parabola, such as one 

 might expect in a work on descriptive geometry. A 

 clearly written chapter on graphical statics might have 

 been introduced here with advantage. Diagrams of 

 bending moment and shearing force are next discussed, 

 and we come to the subject of continuous beams — one 

 of increasing importance. Diagrams of shear and 

 bending for girders with moving loads are then taken 

 up at length, and a model is illustrated showing how 

 the variations in these quantities, as a model loco, 

 passes over a model bridge, may be exhibited to a class. 

 Combined live and dead loads are next considered, 

 and approximations by the introduction of a so-called 

 " equivalent live load " are dealt with at some length 

 in chapter xiii., after which the resistance of a section 

 to bending and shear is discussed, some neat graphical 

 methods of finding the moment of inertia of, and the 

 amount and distribution of shearing force at, a section 

 being explained. 



The very interesting use of the polariscope in in- 

 vestigating internal stress and strain, due to the late 

 Prof. Peter Alexander, is fully described. Questions 

 relating to curvature are next dealt with, the integral 

 calculus being freely used. Amongst all the mass of 

 weighty matter one does not find, so frequently as 

 might be, useful practical rules and results set out 

 clearly in heavy type. For instance, the point of, and 

 amount of, the maximum deflection of a beam fixed 

 at one end and supported at the other, with different 

 distributions of loading, is often wanted in practice — 

 we do not notice it prominently given here. 



Struts, various kinds of trusses, linear arch ribs, &c., 

 are taken up, analytical methods having the promin- 

 ence rather than graphic methods, though the latter 

 are employed to a very limited extent. 



Tables relating to the "two-nosed catenary," the 

 design of segmental arches, and other like matters 

 bring this not at all elementary, yet valuable, work to 

 a close except for an appendix, in which graphic 

 methods are applied to a roof truss — evidently as an 

 afterthought. • R. G. B. 



OUR BOOK SHELF. 



The Principles of Animal Nutrition, with Special 



Reference to the Nutrition of Farm Animals. By 



Henry Prentiss Armsby, Ph.D., Director of the 



Pennsylvania State College Agricultural Experiment 



Station, Pp. vii + 614. (New York: John Wiley 



and Sons; London : Chapman and Hall, Ltd., 1903.) 



Price 17s. 



The growth of institutions similar to that with which 



the classical labours of Lawes and Gilbert in this 



country are associated has been nowhere more marked 



than in the United States of America. The natural 



NO. 1750, VOL. 68] 



advantages of unlimited territory and virgin soil have 

 no doubt much to do with the position of agricultural 

 industry in that country, but added to this has been 

 the recognition by the American people that farming, 

 to be a success, must be conducted on scientific prin- 

 ciples. Our Canadian cousins cannot be said to be 

 behind their neighbours In this respect. The numerous 

 and valuable memoirs which are being constantly 

 issued from these agricultural experiment stations 

 speak much for the Industry and acumen of those en- 

 gaged In conducting and superintending research there. 



Dr. Armsby 's book is a very successful attempt to 

 present the present results of such work, so far as it 

 relates to nutrition, in a systematic manner. It is, 

 however, not a mere handbook for the stock raiser, but 

 win amply repay careful perusal by students of physi- 

 ology. It is a veritable mine of valuable statistics, 

 and nowhere do we remember to have seen more clearly 

 stated the great problems of metabolism and the 

 methods by which they have been, and may be, solved. 

 The law of the conservation of energy is as true for 

 the chemistry of the living organism as it Is for that 

 of the laboratory, and it has been Rubner's epoch- 

 making work to demonstrate that this can be experi- 

 mentally verified. Much in the present book Is 

 naturally taken from Rubner; other names promin- 

 ently quoted are those of Zuntz and Atwater. Refer- 

 ences are given to all Important papers cited, and 

 this materially enhances the value of Dr. Armsby 's 

 book. Where so much Is excellent, it seems rather 

 like carping criticism to point to minor deficiencies. 

 We cannot, however, help noticing that the author's 

 views on the digestion of proteids taken from a book 

 published nearly ten years ago are somewhat anti- 

 quated; Ktihne's theory on the hemi- and anti-products 

 of gastric proteolysis has now been abandoned. The 

 statement, also, that the fat of the food Is absorbed 

 largely in the form of an emulsion requires revision. 

 In connection with the question of uric acid formation, 

 Dr. Armsby does not appear to have grasped the now 

 well-established fact that the formation of this sub- 

 stance in the bird is mainly synthetical, while In the 

 mammal it is mainly, if not entirely, oxidative; he 

 need not, therefore, hesitate to accept the view of its 

 origin from nuclein and purin in these animals. 



We, however, congratulate the author most sincerely 

 on the book as a whole. So many books that one 

 comes across nowadays are repetitions or imitations 

 of others that it is refreshing to come across one which 

 forms a material addition to knowledge. 



Chemical Technology. Vol. iv. Electric Lighting. 

 By A. G. Cooke, M.A., A.M.I.E.E., and Photometry, 

 by W. J. Dibdin, F.I.C., F.C.S. Pp. xviii + 378. 

 (London : J. and A. Churchill, 1903.) Price 205. 



One must not expect too much of a book which aims 

 at treating. In less than 300 pages, the whole subject 

 of electric lighting, from the generation of electric 

 energy in the central station to the manufacture of the 

 lamp for its consumption in the user's house. As a 

 work of reference for technical men engaged in other 

 branches of work, but coming occasionally into contact 

 with electrical engineering, this book should prove 

 useful, just as an article in an encyclopaedia is useful. 

 And just in the same way as an encyclopaedia article is 

 defective, it seems to us that the book before us fails ; 

 by endeavouring to give too much information it only 

 succeeds in giving too little. These objections apply 

 rather to tho scheme of the work than to the way in 

 which Mr. Cooke has carried it out, which is as satis- 

 factory as possible In the circumstances. In some 

 Instances the book Is very much up-to-date ; thus, it is 

 probably one of the first text-books containing a good 

 description of the Nernst lamp, though it is to be 



