o82 Notices respecting New Books. 



Franges cV Interference et Jeurs Applications Metrologiques. Par 

 J. Mace de Lepinay, Professeur a la Faculte des Sciences cle 

 Marseille. Paris: C. Naud. 1902. Pp. 101. (" Scientia " 

 Series, No. 14.) 



Is this interesting and np-to-date brochure the author gives a 

 comprehensive account of the production of interference-fringes, 

 their properties, and application to the exact measurement of 

 length. The last chapter in the book gives a brief account of some 

 determinations of the mass of a cubic decimetre of distilled water 

 at 4 : C. ; and perhaps no better evidence of the value of optical 

 methods of measuring lengths could be obtained than the following 

 concordant results of three recent determinations of this quantity : — 



Mace cle Lepinay 999-954 grammes 



Fabry, M ace de Lepinay and Perot .. 999*974 „ 

 Chappuis 999-976 



Li Electricite Deduite de TExperience et Ramenee au Principe des 

 Travaux Virtuels. Par M.-E. Caryallo. Paris : C. Naud. 

 1902. Pp. 91. ("Scientia''* Series, No. 19.) 



This little book — one of the latest additions to the well-known 

 " Scientia " series — forms an excellent introduction to some of the 

 more difficult portions of Maxwell's great treatise. It is mainly 

 concerned with the application of Lagrange's dynamical equations 

 to electrical problems. The principle of virtual work is employed 

 by the author to establish Lagrange's equations, and the treatment 

 of this subject appears to us to be clearer than any we remember 

 having seen elsewhere. The discussion of the applicability of 

 Lagrange's equations to electrical problems is very thorough, and 

 the interesting case of Barlow's wheel, to which the equations are 

 not applicable, is fully discussed. 



United States Magnetic Declination Tables and Isogonic Charts for 

 1*902. By L. A. Batter, Chief of Division of Terrestrial Mag- 

 netism U.S. Coast and Geodetic Survey. Washington, 1902. 

 Pp. 405, with 2 Charts. 



Terrestrial Magnetism has long formed part of the work of the 

 U;S. Coast and Geodetic Survey, but it has recently been consti- 

 tuted a separate division of the survey under the supervision of 

 Dr. Bauer, well known as the Editor of the journal ' Terrestrial 

 Magnetism.' Judging by the present volume — the first drawn up 

 under Dr. Bauer's regime — there is every prospect of increased 

 activity in magnetic work in the ITnited Skates. The first part of the 

 volume gives a lengthy historical account of the origin and progress 

 of the subject, commencing with a resume of what is believed to 



