Notices respecting New Books. 177 



Physikalisches Praktikum. Mit besonderer Beruclcslchtiyung der 

 physikalisch-chemischen Methoden. Von Eilhard Wiedemann 

 mid Hermann Ebert. Braunschweig: F. Yieweg uud Sohn, 

 1899: pp. xxx. + 574. 



The fact that this book is now in its fourth edition may betaken 

 as a sufficient guarantee of its general excellence. One of its 

 special features is the attention given to measurements which are of 

 importance in chemical investigations, such as the determination of 

 vapour-densities, melting-points, boiling-points, heats of neutral- 

 ization &c. Thearrangemenfcof thesubjectmatteris strictly method- 

 ical, the general plan followed consisting in prefacing each section 

 by a brief yet lucid account of the principles involved, then 

 describing the apparatus used, and finally giving directions for 

 carrying out a number of measurements. Great credit is due to 

 the publishers for the beautiful engravings illustrating the various 

 forms of instruments and apparatus described in the book ; it is 

 not -often that such a uniformly high standard of excellence is 

 maintained in this respect. 



In a few of its details, the book would appear to be capable of 

 some degree of improvement. Thus, it is extremely doubtful 

 whether the section dealing with the "proof "of Ohm's law is con- 

 ducive to clearing up a student's ideas on this subject. A "proof" 

 of the law which involves the use of an electromagnetic voltmeter can 

 hardly be taken seriously. Again, we regret to notice that the 

 authors appear to use the terms " electromotive-force " and " poten- 

 tial difference " indiscriminately; this pernicious habit is productive 

 of not a little confusion in the mind of a student. In the section 

 on photometry, the form of Lummer and Brodhun photometer 

 described is not the latest type of this instrument, but is an early 

 form, which has since undergone considerable modifications. 



In spite, however, of a few defects such as those noticed, there 

 are probably few books on the subject which contain so large a mass 

 of up-to-date and reliable information in so small a compass, and so 

 attractive a form. The student who conscientiously works through 

 the book and carries out the experiments described in it, will have 

 acquired a very sound knowledge of physical processes and measure- 

 ments. The tables and formulae given at the end of the book 

 should prove extremely useful. The copious table of contents at 

 the beginning and the index at the end of the book also deserve a 

 word of praise. 



The, Kinetic Theory of Gases. By Dr. Oskar Emil Meyer, 

 Translated from the second revised edition by B.OBERT E. Batnes. 

 M.A. London: Longmans, GreeD, & Co. 1899 : pp. xvi.-j- 472. 



Until comparatively recently, the whole of the literature dealing 

 with the subject of p hysics could be divided into two sections : 

 works dealing with the elements of various branches of the science, 



Phil. Mag. S. 5. Vol. 50. No. 302. July 1P00. N 



