September i6, 1909J 



NA TURE 



more satisfactory manner than is usually the case in 

 text-books on mechanics. The book is certain to 

 prove a useful one to all those who are engaged in 

 teaching the subject of mechanics to engineering 

 students, and the number of well-selected examples 

 makes it a particularly satisfactory book for the 

 student himself. Many young engineers are far away 

 from help in matters of this nature, and have to depend 

 upon their own resources — it is essential in such a 

 case that they should have a large number of practical 

 pioblems to work through in order to familiarise 

 themselves with the principles underlying each branch 

 of the subject. 



(2) This book has been written specially for artillery 

 officers detailed for duty in ordnance factories; it is 

 copiously illustrated, and special attention has been 

 given to the relative advantages and disadvantages of 

 different types of machine tools, and to different 

 methods of transmitting motion to the tools. 



The first section is devoted to such details as the 

 transmission of motion from one shaft to another by 

 belting and gearing, quick return motions, cams, 

 sliding pairs, turning pairs, and screw pairs, and in 

 each case brief notes are given as to the important 

 points to which attention should be paid in order to 

 secure good results and to maintain all working parts 

 in good order. 



The second section deals with all the more impor- 

 tant machine tools which are to be found in a modern 

 workshop ; in each case a regular order of treatment 

 is followed — first the parts exterior to the machine 

 itself and transmitting motion to it are discussed, and 

 then in order the links in the machine receiving this 

 motion, the links of the machine transmitting move- 

 ment to the work, the links of the machine trans- 

 mitting movement to the cutting tool, and lastly any 

 other specialised link, ' and the frame. This is a 

 method of treatment suitable not only for the non- 

 technical student, but also for students who are just 

 beginning the study of machines and machine tools, 

 and the illustrations, which form a special feature of 

 the book, are so arranged that the reader has no diffi- 

 culty in finding at once in any of the figures the 

 link of the machine which is described in any 

 particular paragraph of the written description of the 

 machine. 



The third section deals with the cutting tools used 

 in the various types of machine tools, methods of 

 tempering, angles for the cutting edge for different 

 classes of work, methods of lubrication, and speed of 

 cutting are all discussed in detail, and a few para- 

 graphs are devoted to the employment of the new 

 high-speed steels. 



In view of the fact that interchangeabilitv of parts 

 is now so important in all cases where large numbers 

 of similar machines are constructed, the fourth section 

 is entirely given up to an account of the construction 

 and use of various types of gauges, with a series of 

 viseful notes on the precautions which must be adopted 

 to ensure that their eniplovment shall secure the 

 desired result. The book should be consulted by all 

 those who are engaged in the design of machine 

 tools. T. H. B. 



NO. 2081, VOL. 81] 



A BELGIAN BOTANIST. 

 Notice siir Leo Errcra. By L. Fredericq and J. 



Massart. Pp. 153. (Bruxelles : H. Lamertin ; 



London : Williams and Norgate, 1908.) 

 Rccueil d'CEuvrcs de Lio Errcra. Vols. i. and ii. 



Botanique generale. Pp. iv + 318 and v + 341. Vol. 



iii. Melanges Vers et Prose. Pp. xiv + 222. 



(Bruxelles : H. Lamertin ; London : Williams and 



Norgate, 1908-9.) 



IT would be difficult to overestimate the influence 

 of the two great German professors, Anton De 

 Bary and Julius Sachs, on the progress of botany. 

 .At a time when many fundamental ideas were only 

 beginning to take shape, these advanced workers and 

 leaders of thought attracted a succession of brilliant 

 students from many European countries, who 

 absorbed in Strassburg and ^^■urzburg the doctrines 

 and inspirations of their masters, and eventually 

 spread abroad the new theories and conceptions that 

 are now regarded as the foundations of botanical 

 science. Amongst this band of eager students was 

 the Belgian, Leo Errera, who entered first De Bary's 

 laboratory in 1897, and subsequently sought further 

 experience under the tutelage of Sachs. Two import- 

 ant results can be traced to these courses of foreign 

 study. In the first place, intercourse with such gifted 

 teachers and with brilliant colleagues helped to stimu- 

 late the energies of an already keen enthusiast, and 

 to pave the way for future friendships and associa- 

 tions. In the second place, his interests were diverted 

 from systematic to chemico-physiological botany, 

 which became one of the chief lines of research at. 

 the University of Brussels. 



The first of his primary contributions to science 

 was the paper on glycogen in the Mucorinea;; this, 

 was the outcome of research in De Bary and Hoppe- 

 Seyler's laboratories, and required a profound know- 

 ledge of the two sciences of botany and chemistry. 

 It was followed ^v other papers on the same and 

 other physiological subjects published by himself or 

 his students. Prof. Errera was also well versed in 

 mathematics and physics, evidence of which is fur- 

 nished by the course of molecular physiology pre- 

 pared for his advanced students. The researches con- 

 nected with glycogen and the localisation of alkaloids, 

 the papers on the application of physical chemistry- 

 to the elementary phenomena of cells, the relations 

 of flowers and insects, and the defensive structures 

 of plants, may be regarded as his chief contributions 

 to botany. 



As a professor, Errera took the keenest interest 

 in his students, and spared no pains to stimulate 

 their energies towards the acquirement of knowledge 

 and the prosecution of research. At the time when 

 practical courses were not yet customary he initiated 

 a course which was first held in two small rooms in 

 the gardens, and later in a more spacious laboratory 

 provided at his own expense in a neighbouring build- 

 ing. The biography compiled by two of his former 

 students bears testimony to the enthusiasm he in- 

 spired, and provides a realistic picture of his varied 

 talents. ■ He was an accomplished linguist, an excel- 

 lent lecturer, and an entertaining companion. 



