124 



NATURE 



[June ii, 1903 



interests are perhaps too multifarious, for one or two 

 of his papers seem to have come into print before the 

 observations they contain were ripe for publication. 



Nothing, however, could be more elaborate or pains- 

 taking than the opening article, a study of the dietary 

 of the labouring classes of Edinburgh, of which the 

 expenses were partly defrayed by the progressive Town 

 Council. The details were procured by a band of lady 

 students, and are often amusing if not always essential. 

 Thus we are glad to learn that a lady who dresses " in 

 the Canongate fashion of a loose blouse " gets on well 

 with her neighbours, but tragic possibilities follow on 

 our introduction to the husband; " Mr. T. is not a 

 teetotaler and he smokes." 



The most interesting result of the study is the start- 

 ling discovery that porridge is rapidly disappearing as 

 a staple article of diet with these people. In fact, the 

 investigation might have been entitled " A Plea for 

 Porridge," for the authors rightly insist upon its 

 economic value. 



Of the other articles, the longest is a contribution 

 to the histology and metabolism of the foetus and 

 placenta of the rabbit, by Dr. Chipman. With so 

 difficult a subject, and so confused a terminology, the 

 author's lucidity of style is very welcome, and the 

 illustrative microphotographs, numbering no less than 

 186, are eloquent of his sincerity. He throws light on 

 inany controversial points, e.g. the manner of first 

 contact of the embryonic and maternal tissues, the 

 ■" unequivocal differentiation " of these two tissues, and 

 ithe relations of placental and foetal glycogen. It is a 

 pity that he says nothing of the glycogen in the foetal 

 muscles, where it is said to exist sometimes to the ex- 

 tent of 40 per cent, of the dried tissue. There is much 

 about the formation of " fibrinous tissue " from extra- 

 vasations of blood, but he ligatured the vessels at the 

 •outset to ensure, as he explains, an injection of the 

 placentae, and we would suggest that these extravasa- 

 tions may have been, in part, an artefact. 



Dr. Rainy 's paper on the action of diphtheria toxin 

 on nerve cells is so excellent, so far as it goes, that we 

 look forward to a further instalment next year. He 

 obtains very definite intracellular effects, and avoids 

 error by a most thorough series of controls. Also he 

 gives an admirable history of the subject. 



There are many other minor articles of varying 

 value. Dr. Carmichael, working at the infections of 

 the gall-bladder, injected microorganisms into a 

 mesenteric vein in five rabbits, and since he gets, but 

 one positive result, he concludes that infection can 

 occur only by direct extension or by the cystic artery ; 

 K3f such factors as the virulence of the organism, the 

 nature of the animal, and the condition of the gall- 

 bladder he takes no account. 



We are glad to see that Miss Huie is continuing her 

 observations on the histology of cell-metabolism which 

 she began so successfully in Oxford. Dr. Dunlop, in 

 some observations on prison diets, confirms Atwater's 

 finding that Voit's classical standard of diet is too low. 

 Finally, we would mention a curious study by Dr. 

 Berry in comparative morphology, in which he con- 

 cludes that the vermiform appendix is not vestigial 

 but the summation of a long development. 

 NO. 1754, VOL. 68] 



OUR BOOK SHELF. 



An Elementary Treatise on the Mechanics of 



Machinery, with Special Reference to the Mechanics 



of the Steam Engine. By Joseph N. Le Conte. 



Pp. xi + 311 ; with 15 plates. (New York : The Mac- 



millan Company; London: Macmillan and Co., 



Ltd., 1902.) Price los. 6d. net. 

 The author states that this book is the outcome of a 

 series of lectures given to engineering students in the 

 University of Califprnia. 



In an introductory chapter relating to uniplanar 

 motion, some properties of instantaneous centres and 

 centrodes are given, and methods are set out of deter- 

 mining relative velocities, both linear and angular. 



The next part is devoted to machinery of trans- 

 mission, comprising rigid and flexible couplings, fric- 

 tion gearing, belt and rope gearing, and toothed gear- 

 ing, the shafts being parallel, intersecting, or crossing, 

 respectively. This part also includes chapters on 

 parallel motions and cams. 



The author has a leaning towards analytical rather 

 than graphical treatment, and prefers accurate and 

 complete investigations to simplified appro.ximations. 

 This is apt to result in formulae which convey little 

 meaning, and which repel by their complexity, requir- 

 ing the subject-matter to be of great importance to 

 justify their use. Thus in the discussion on wheel 

 teeth there is an investigation into the equation to the 

 profile which shall correspond with any given curve of 

 action ; and formidable expressions are given for cal- 

 culating the angles of action in cycloidal and involute 

 teeth. We should like to have seen these supplemented 

 by graphical methods, using tracing paper and a 

 pricker, after Mr. Last, whereby wheel teeth can be 

 set out with perfect accuracy, with the minimum of 

 trouble, and in such a way as to bring very prominently 

 into notice the nature of the action between a pair of 

 teeth. 



Part iii. deals with the steam engine, the first chapter 

 relating to the kinetics of the "piston-crank chain." 

 Accurate formulae are established giving the position, 

 velocity and acceleration of any point moving with 

 the connecting rod referred to the crank position, from 

 which are deduced the special values for the centre of 

 mass, the crosshead and crank pin. Formulae tor 

 angular motions of the connecting rod are also given. 

 In this chapter the simple and gridiron slide valves 

 are considered, and also the Meyer and Thompson 

 gears, Zeuner's valve diagram being used along with 

 the formulae. 



Chapter ii. of this part is taken up with the dynamics 

 of the steam engine, and investigates piston and crank 

 efforts, inertia effects, counterbalancing, and the 

 actions of the fly-wheel and governor. The formulae 

 of the preceding chapter are used to calculate the force 

 actions in a small horizontal engine due to acceler- 

 ation of the connecting rod for a number of points in 

 the cycle; these are tabulated, and the results plotted 

 in plates at the end of the volume. 



In the mechanics of the steam engine, the use of 

 the Fourier development, with the conception of rota- 

 ting vectors, is preferable to the method adopted 

 by the author. The series converges so rapidly that 

 it is seldom necessary to go beyond the second or 

 octave term, and a very clear view is obtained of the 

 secondary actions due to obliquities of the connecting 

 and eccentric rods. 



The principle of balancing the forces on the crank- 

 shaft of an engine, ignoring those on the frame, is 

 novel, and leads to curious results in the case of the 

 Southern Pacific locomotive selected by the author as 

 an example. 



The investigation of the action of fly-wheel governors 

 seems very complete, and is worth study. 



