Notices respecting New Books. oil 



ture absolutely, we must assume that some property of a substance 

 remains, constant at that temperature and at other known tempe- 

 ratures. If this is not the case, the same temperature will have 

 different values according to the method by which it is measured, 

 and its true value will most probably be that found by a majority 

 of the methods. The author in his present volume has criticized 

 the different methods of determining temperatures, and has given 

 the results of experiments by himself and other workers in the 

 same field, from which it appears that only three properties remain 

 constant over wide ranges of temperature. These are the expan- 

 sion of gases, the change of their viscosity with temperature, and 

 the thermoelectric properties of certain metals. All these methods 

 yield consistent results for the value of a given high temperature. 



The second part of the volume is a discussion of the applicability 

 of these three methods, and Dr. Barus pronounces in favour of the 

 thermoelectric method. He then goes on to discuss the various 

 forms of apparatus which might be used in applying this method ; 

 from which it appears that a junction of platinum with an alloy of 

 platinum and iridium or rhodium gives the best results. 



The book is the outcome of several years of difficult experi- 

 menting, and it is to be hoped that it will encourage a closer study 

 ot the properties of bodies, and especially of metals, at high tem- 

 peratures. James L. Howakd. 



Billfsbuch filr die Ausfuhrung ele/ctrischer Messungen. By Dr. Ad. 

 Heydweiller. Leipzig: Barth, 1892. 



This volume is not intended to serve as a text-book, but merely as 

 an epitome of the various processes of electrical measurement. It 

 gives in a collected form the different methods available for any 

 particular kind of measurement, together with a short description 

 of each ; the formulas necessary in order to calculate the results 

 being likewise quoted, but not proved. In the majority of cases, 

 however, the original papers and treatises are referred to for more 

 complete information on this latter point. Under each experiment 

 the author mentions the sources of error to which it is liable, and 

 the devices for avoiding or eliminating them are stated, when such 

 exist. This portion of the work has been carefully written, and 

 will be found useful when the choice of a suitable method of 

 measurement has to be made. At the end of the volume the 

 various electrical constants have been tabulated, and four-figure 

 logarithm and trigonometrical tables are also to be found there. 

 Although the title of the book refers to electricity only descriptions 

 of magnetic observations have also been given ; but, as the author 

 tells us in his preface, these are treated more briefly, and only 

 those which are necessary in electrical measurements have been 

 described. James L. Howard, 



