76 Notices respecting New Boohs. 



definition connects magnetism with electricity clearly p may have 

 dimensions, but the electrostatic and electromagnetic theories each 

 assume it to be a mere number. The result of retaining p is 

 to make p 2 /fjuc the square of a velocity. 



Chemists will probably regret that the subjects of migration of 

 ions, ionic velocity, and electrolytic conductivity find no place in 

 the volume, electrolysis being treated in a very elementary 

 fashion. The chapter devoted to dielectric currents and the 

 electromagnetic theory of light is very readable, even by those who 

 are not familiar with the ordinary equations of wave propagation ; 

 it contains a concise though somewhat brief account of the recent 

 confirmations of Maxwell's theory by Hertz and others. We 

 notice that the discovery of the action of electric waves in dimin- 

 ishing the resistance of a tube of metal turnings is erroneously 

 attributed to Prof. Lodge : the experiment was originally de- 

 scribed in this form by M. Branly. 



The volume is nicely printed, with bold headings at the com- 

 mencement of each section, and is of a handy size for students' 

 use. There is a subject-index at the end of the book, but a list of 

 titles of the various chapters inserted at the commencement of the 

 volume would be of great service to the student. 



James L. Howard. 



An Exercise Book of Elementary Physics for Organised Science 

 Schools etc. ; arranged according to the Headmasters' Associations 



Syllabus of Practical Physics. By Richard A. Gregory, 



F.B.A.S. London : Macmillan & Co., 1895. 

 The Government having at last recognized the suitability of 

 elementary practical physics and mechanics as school subjects, this 

 series of exercises suggests a method of making such subjects 

 effective in training students to acquire habits of observation, 

 accuracy, and carefulness. The exercises include the general 

 operations of weighing and measuring, mechanics and heat ; they 

 are arranged according to subject and in order of difficulty. 

 Spaces are provided in which the results of experiments may be 

 recorded, and in each case the student is left to make his own 

 deductions from his experiments. 



Some of the directions for experiment are not very explicit : 

 for example, in order to measure the rise of water in capillary 

 tubes the student is told to take two very narrow uibes, one having 

 twice the internal diameter of the other, and to wash them by 

 drawing distilled water through them. A good student, ard rot a 

 few teachers, will want to know how the diameters of the tubes 

 are to be measured ; and the results of the experiment will not be 

 very satisfactory unless the tubes have been previously washed 

 with some cleansing agent, such as potash or alcohol. A few 

 exercises on glass-blowing, soldering, and similar manipulation 

 might be added with advantage. The construction of the model 

 lift or force-pump, used in one of the experiments, would be 

 excellent practice in this direction. 



