82 Scientific Intelligence. 



radiations of longer wave-length than the bands (such as X-ray- 

 lines) depends upon the silver bromide molecules, just as for 

 ordinary light. 



In an earlier investigation Wagner found a close connection 

 between the wave-length A^ of the sharp edges of the bromine, 

 silver, and tin bands and the wave-length Ao of the corresponding 

 fluorescence lines of Moseley's iT-series. Moreover, conformable 

 to the law of Stokes, the radiation of longest wave-length able to 

 produce fluorescence was always more refrangible than the excited 

 _Ka-line. Finally, the ratio X A /Xa (" der Stokessche Sprung") 

 was approximately constant. In addition to the three substances 

 mentioned above the investigation has been extended by Wagner 

 to the following metals, namely : cadmium, copper, iron, nickel 

 and palladium. All of the relations between the wave-lengths 

 were found to hold, and a number of new facts of theoretical sig- 

 nificance were brought to light. For further details, however, 

 the original paper must be consulted. — Ann. d. Physik, vol. xlvi, 

 p. 868, March, 1915. h. s. it. 



7. Elements of Optics ; by George W. Parker. Pp. 122, 

 with 64 figures. London, 1915 (Longmans, Green, and Co.). — 

 That the text is very elementary in character may be inferred 

 from the following quotation, namely: "This little book is 

 intended for those students whose knowledge of Mathematics is 

 limited to an acquaintance with Elementary Geometry, the solu- 

 tion of Simple Algebraic Equations, and a few fundamental propo- 

 sitions in Trigonometry." The author's style is clear, and the 

 material is so chosen as to be interesting as well as instructive. 

 The method of rays is used throughout and the illustrative figures 

 are printed as white lines on black background. A comparatively 

 large number (106) of "exercises" for solution by the student are 

 incorporated in the text and the answers are given at the end of 

 the volume. The book is undoubtedly good, as far as it goes, but 

 the impression of incompleteness is given by the unusually small 

 number of topics discussed. Nothing is said, for example, about 

 photometry, astigmatism, etc. h. s. u. 



8. Dielectric Phenomena in Sigh Voltage Engineering • by 

 F. W. Peek, Jr. Pp. xv, 265, with 190 figures. New York, 1915 

 (McGraw-Hill Book Co.). — " It is the object of the author to give 

 in this book the properties of gaseous, liquid and solid insulations, 

 and methods of utilizing these properties to the best advantage in 

 the problems of high-voltage engineering." " Much original 

 work is given, as well as reference to other investigations." 

 "The author's extensive research was made possible by facilities 

 afforded by the Consulting Engineering Department of the Gen- 

 eral Electric Company . . ." 



A general idea of the contents of the volume may be obtained 

 from the titles of the chapters, namely : "The Dielectric Field 

 and Dielectric Circuit (Mathematical Consideration) ; Visual 

 Corona ; Spark-over; Corona Loss; Corona and Spark-over in Oil 

 and Liquid Insulations; Solid Insulation ; The Electron Theory ; 



