May 15, 19 1 3] 



NATURE 



Many passages of particular interest might be 

 quoted from all of the chapters, but as the book 

 to be appreciated must be read as a whole, we 

 would rather commend it warmly to students of 

 natural history and to those who would know of 

 Britain's worthies. Thanks to the diaries kept by 

 our earliest botanists and from the free use of con- 

 temporary information, the biographies are full of 

 living personal interest. We can picture Robert 

 Brown — facile botanicorum princeps, Britannia; 

 gloria et ornamentum — all the more easily and 

 truly from the human touches in the following 

 extracts from his diary for two consecutive days : 



" Feb. 7. — Before breakfast began the German 

 auxiliary verbs. ... At dinner about 3 pints of 

 port . . . slept in my chair till nearly 3 in the 

 morning. 



" Feb. 8. — Before breakfast finished the auxiliary 

 erb Seyn; to be. . . ." A. W. H. 



PRACTICAL AND THEORETICAL PHYSICS. 

 • I lie Essentials of Physics. By Prof. G. A. 

 Hill. Pp. viii + 346. (New York and London: 

 Ginn and Co., n.d.) Price 5s. 



(2) Practical Measurements in Radio activity. By 

 Dr. W. Makower and Dr. H. Geiger. Pp ix + 

 151. (London: Longmans, Green and Co., 

 1912.) Price 5s. net. 



(3) A Systematic Course of Practical Science for 

 Secondary and other Schools. By A. W. Mason. 

 Book I., Introductory Physical Measurements. 

 Pp. vii+126. (London: Rivingtons, 1912.) 

 Price is. 6d. net. 



(4) Practical Physics : a Text-book for Technical 

 Schools and Colleges. By Angus McLean. Pp. 

 xi 4-402. (London: Adam and Charles Black, 

 1912.) Price 75. 6d. net. 



(5) .4 Course of Elementary Practical Physics. 

 By H. V. S. Shorter. Part i., Mensuration, 

 Mechanics, Hydrostatics. Pp. in. Price 2s. 

 Part ii., Heat and Light. Pp. 216. Price 3s. 

 (Oxford : Clarendon Press, 1912.) 



(6) Lehrbuch der Physik fur Mediziner und Bio- 

 logen. By Dr. Ernst Lecher. Pp. vii + 451. 

 (Leipzig and Berlin: B. G. Teubner, 1912.) 

 Price 8 marks. 



(7) An Introduction to Mathematical Physics. By 

 Dr. R. A. Houstoun. Pp. ix+199. (London: 

 Longmans, Green and Co., 1912.) Price 6s. net. 



(8) Die Elektricitat. By Prof. F. Adami. 

 ( Ihicher der Naturwissenschaft, herausgegeben 

 von Prof. S. Giinther.) 9 und 14 Band. Pp. 



1264-4 plates + 1804- 12 plates. (Leipzig: 

 Philipp Reclam, jun., n.d.) Price 1.50 marks. 



()' 



commencing instruction in every 

 branch of knowledge. The correct solution of the 

 NO. 2272, VOL. 91] 



problem is of much importance, particularly in 

 physics, in which subject, for some reason, 

 students seem to find more than average difficult). 

 The author of this book has been convinced by his 

 teaching experience that the most efficient method 

 of presenting the elementary principles is by means 

 of question and answer. His book therefore con- 

 sists entirely of a long series of questions. To the 

 more difficult of these questions answers are ap- 

 pended : to the easier the student is expected 

 to supply his own answers. The subjects treated 

 are just those usual in an elementary text-book, 

 the greatest stress, however, being laid on mech- 

 anics, to which about half the book is devoted. 



While not questioning the undoubted value of 

 question and answer in ascertaining the progress 

 of students, it cannot be admitted that these form 

 the function of a text-book. Question and answer 

 should preferably be oral ; they should also be 

 mutual as between teacher and student. As a 

 text-book the present volume is comparatively 

 useless, principally on account of the lack of con- 

 tinuity and logical order which the method of 

 presentation involves, but as a book of examples 

 it may prove of considerable value. 



(2) The appearance of a book on radio-active 

 measurements is very welcome. That it should 

 come from the laboratory of Prof. Rutherford, 

 and have for its authors two such distinguished 

 workers on radio-activity, practically ensures its 

 general adoption in advanced physical laboratories. 

 It can scarcely be doubted that the authors' 

 assurance that so many and varied exercises in 

 radio-activity can be performed with comparatively 

 small quantities of active material will lead to the 

 introduction of such measurements into the labora- 

 tory courses of many honours schools in physics. 

 Most of the experiments described are already so 

 included in Manchester, particularly with the view 

 of the students ultimately taking up original 

 research in this subject. 



The earlier part of the book is devoted to the 

 theory and practical use of the electrometer and 

 various electroscopes, and the treatment is both 

 detailed and lucid. Much useful advice in the con- 

 struction of home-made instruments is given, and 

 the student is also told how to surmount the 

 various difficulties which arise. Chapters iii. to vi. 

 are devoted to the practical exercises previously 

 referred to, the number which can be performed 

 by means of simple apparatus being surprisingly 

 large. 



The remainder of the book is intended for 

 original investigators rather than ordinary 

 students. Here the methods of making accurately 

 standard radio-active measurements and the 

 separation of radio-active substances are treated 



