436 Notices respecting New Books. 



Repeated trials showed that the sounds produced were in no way 

 altered by the fact of the wire being in the magnetic field. 



The former method of the trace on smoked paper has been 

 used by me in the Millard Laboratory for getting traces of 

 the expansion and contraction of bars of different metals up to 

 2 centim. diameter, heated over a part of their length in a 

 gas furnace. 



San Rerno, March 28, 1891. 



LIV. Notices respecting New Books. 



A Dictionary of Metric and other useful Measures. By Latimer 



Clark, F.R.S. (London : E. & F. N. Spon.) 

 /^NE of the most marked characteristics of the progress of Science 

 ^-^ is to be found in the gradual decay of the old rule of thumb 

 methods of calculation formerly in use among practical men. 

 The development of scientific methods in all branches of commerce 

 necessitates not only a greater, but also a more accurate, know- 

 ledge of the relations between the units of measurement in various 

 trades and in different countries. Also the daily increase in the 

 number of practical applications of electricity has caused attention 

 to be directed to its units of measurement ; and it is to be hoped 

 that the simplicity of these units will lead finally to their universal 

 adoption. 



In the volume before us Mr. Clark has arranged all the principal 

 units of measurement in alphabetical order and given definitions of 

 each ; he has also given multiplying factors for the conversion 

 from one system of units to another. For those who prefer 

 logarithmic computations the logarithms of these factors are given 

 with five-figure accuracy, and a table of five-figure logarithms is 

 also added at the end cf the book. The work is very complete 

 and has been brought quite up to date, the mass of a cubic inch of 

 water for example being given as 252-286 grains as legalized by 

 the Board of Trade in 1890, thus displacing the previous number, 

 viz., 252-458 grains. The units given include almost all in com- 

 mercial use, and range from the law-writer's " folio " to the unit of 

 self-induction. The apothecaries' weights and measures have not 

 been forgotten, and should prove useful to many a photographer. 

 The alphabetical arrangement is very convenient, and any required 

 unit can be found at once. The book is, moreover, for a work of 

 this kind, singularly free from errors. Its figures are printed in a 

 good, bold type, very unlike that of the familiar engineers' and 

 electricians' pocket-books, but none the less commendable. 



James L. Howard. 



Index of Spectra. By W. Marshall Watts, D.Sc, F.I.C. 



(Manchester : Abel Hey wood & Son.) 



This book appears as a revised aud greatly enlarged edition of 



the original work with the same title, which was published in 



