556 



NATURE 



[April i6, 1908 



gravity, the latter being somewhat extensively applied, 

 including Guldinus's rules and mensuration problems. 

 The concluding chapters relate to forces and jointed 

 frames in two and three dimensions, with examples 

 or roof and bridge trusses and cranes. 



The general plan of the book is good, the endeavour 

 b -ing to " lay stress on the practical utility of the 

 science " rather than on "rigour of deduction." In 

 carrying out this very laudable idea, the authors, 

 through lack of practical experience, sometimes err 

 by giving drawings like that of the safety-valve on 

 p. 242, in which the constructional details are almost 

 offensively crude, or by giving examples like No. i6, 

 p. 140, where the efficiency of a Weston differential 

 pulley-block is stated to be 80 per cent., or like No. 38, 

 p 77, in which a rail, supported at the ends and 

 loaded as a beam at the middle, is said to be bent 

 into a circular arc. In spite of these minor defects, 

 however, the book can be recommended as affording 

 ail excellent introduction to statics. 



{3) The general character of this work places 

 it somewhere between the engineering pocket- 

 book and the college text-book. The methods, 

 formulae, and appliances which a student encounters 

 during a good college course in mechanical engineer- 

 ing are here, not demonstrated, but collected and 

 described, systematically, and applied to such prac- 

 tical examples as are likely to occur in an engineering 

 workshop. In section i. the subject-matter comprises 

 arithmetical, graphical, and mechanical computations, 

 by modern abbreviated methods, and includes tech- 

 nical mensuration, the use of the slide-rule and the 

 planimeter, and mathematical tables. In section ii. 

 we have laboratory experiments and calculations re- 

 lating to machines, acceleration, momentum, force, 

 work, energy, and power. Section iii. relates to 

 boilers and heat engines, considered both from the 

 thermodynamical and constructional point of view, 

 with a chapter on the cost of motive power. These 

 three sections are well adapted for students who have 

 passed from college to practical work, in helping them 

 to recall their theoretical knowledge as occasion may 

 require. A good collection of examples will be found 

 for practice. The style is perhaps somewhat diffuse, 

 and there are a few minor defects, but this portion of 

 the book will be appreciated in many quarters. 



The fourth and concluding section, however, is of 

 most interest and value. It deals with the business 

 side of engineering, a branch that is beyond the 

 usual college course, yet of paramount importance to 

 the young aspiring engineer. The subjects discussed 

 are the commercial aspects of engineering ; the quali- 

 fications and duties of the works manager; the calcu- 

 lation of weights and the preparation of estimates and 

 bills of costs ; and the bonus and premium systems of 

 wages. The authors give some most striking 

 examples of the great value of squared-paper work in 

 the systematic plotting of variable quantities in all 

 branches of a manufacturing establishment, and the 

 lessons to be learnt therefrom. This section is ex- 

 tremely suggestive, and will well repay the careful 

 study of all practical engineers. 

 NO. 2007, VOL. 77] 



MULTUM IN PARVO. 

 (i) Die Tier7velt des Mikroskops (die Urtiere). By Dr. 

 Richard Goldschmidt. Pp. iv+ioo; 39 figures. 

 (Leipzig: B. G. Teubner, 1907.) Price 1.25 marks. 



(2) Das Siisswasser-Plankion. By Dr. Otto 

 Zacharias. Pp. iv-l-130; 49 figures. (Leipzig: 

 B. G. Teubner, 1907.) Price 1.25 marks. 



(3) Befruchtung iiiid Vererbung im Pflatizenreiche. By 

 Prof. K. Giesenhagen. Pp. iv+132; 31 figures. 

 (Leipzig: Quelle and Meyer, 1907.) Price 1.25 

 marks. 



(4) Das Werdeii iind Vergehen dcr Pflanzcn. By Prof. 

 P. Gisevius. Pp. 132 ; 24 figures. (Leipzig : B. G. 

 Teubner, 1907.) Price 1.25 marks. 



(5) Das Schmarotzertmn im Ticrreich iind seine Bedeut- 

 iing fiir die .irtbilditng. By Prof. Ludwig von Graff. 

 Pp. iv+132; 24 figures. (Leipzig: Quelle and 

 Meyer, 1907.) Price 1.25 marks. 



(6) Die Meclianik des Geisteslchens. By Prof. Max 

 Verworn. Pp. iv+104; 11 figures. (Leipzig: B. G. 

 Teubner, 1907.) Price 1.25 marks. 



IT was Leibniz who said that the more science 

 advances the more it will be expressed in little 

 books. If that is so, the recent abundant crop of 

 primers may be regarded as a healthy sign — especially 

 when we find that many of them are very good. It 

 need hardly be said that an introduction to the study 

 of parasitism by von Graff, or to the study of fresh- 

 water plankton by Zacharias, cannot fail to be useful 

 and stimulating. There is also an economic side to 

 the phenomenon presented by the bundle of primers 

 before us. It seems as if the great encyclopaedias, 

 which were relatively costly, were being replaced by 

 these cheap booklets. Instead of saving up to purchase 

 the huge volume P, containing much that he does 

 not want, the student can buy at a shilling each 

 three little treatises on parasitism, plankton, and 

 protozoa. This expresses a democratisation of scien- 

 tific literature, with its familiar analogue in the 

 popular " sixpennies. " 



(i) In a clear and precise way, Dr. Richard Gold- 

 schmidt tells the story of the Protozoa — how they came 

 to be known, where they are found, how they live, 

 what part many of them play in the economy of the 

 sea, what they have done in building up chalk cliffs 

 and the like, and how they come into close quarters 

 with man in malaria and sleeping sickness, and other 

 diseases. With the aid of excellent figures, most of 

 which are familiar, and some of which, like Max 

 Schulze's Polystomella, could hardly be improved upon, 

 the author introduces the student to the rhizopods, the 

 infusorians and Sporozoa, and although the book will 

 not, of course, enable the observer to identify many 

 of the Protozoa which he may discover, it will help 

 him to understand them and to realise how many 

 problems even the common amoeba still raises in a 

 reflective mind. 



(2) The indefatigable director of the biological 

 station at Plon deals with a subject to the study of 

 which a great part of his life has been honourably 

 devoted — the fresh-water plankton. His treatment of 



