JuNi; 4, 1915] 



SCIENCE 



829 



his work in the physical laboratory and ac- 

 quire some facility in determining the ac- 

 curacy and significance of his measurements. 

 A. DE Forest Palmer 



Electric Arcs. By Clement D. Child, Ph.D., 



professor of physics, Colgate Unirersity. 



New York, D. Van ISTostrand Company. 



1913. Pp. 194. 



A text of this kind must interest at least 

 two classes of readers ; those who wish to know 

 more of the physics of the electric arc and 

 those who are intensively engaged in arc lamp 

 development. The author has digested the 

 results of those investigations made since the 

 publication of Mrs. Ayrton's " The Electric 

 Arc," which contains a similar digest of the 

 investigations made previous to 1898. 



In the first six chapters the author discusses 

 the relations between terminal voltage, cur- 

 rent, resistance and E.M.F. of pure carbon, 

 impregnated carbon, pure metal and metallic 

 oside arcs operated with direct and alternating 

 current in air and in various gases at differ- 

 ent pressures. This discussion also includes 

 the performance of the mercury arc rectifier 

 and the mercury arc lamp under various con- 

 ditions. 



The seventh chapter, headed "Photometry 

 of the Electric Arc," contains information re- 

 garding the light-producing properties of vari- 

 ous electric arcs and scarcely touches upon the 

 measurement of light suggested by the caption. 

 The following chapter contains a brief review 

 of the use of the electric arc in wireless tele- 

 phony. All hypothesis regarding the electric 

 arc is reserved for the last chapter, where the 

 author offers an explanation of certain arc 

 phenomena in the ionic theory. 



The book would take on added interest from 

 the scientific viewpoint if it contained refer- 

 ences to the action of electric arcs between 

 metal terminals in liquids such as alcohol, 

 mineral oil, carbon-tetrachloride, etc., or high 

 tension arcs in air. Although the book title 

 suggests a more general discussion the author 

 pays more attention to the "light-producing 

 electric arc." 



The text includes an extensive bibliography 



to which detailed references are made at the 

 appropriate place. The continuity of the dis- 

 cussion is increased by the results of the au- 

 thor's own investigations whenever the reports 

 of others failed to reveal the required data. 

 Thoroughness and presentation of many 

 viewpoints characterize the text throughout. 

 To the student interested in electric arc phe- 

 nomena a careful reading of Mrs. Ayrton's 

 text followed by that of Dr. Child should prove 

 an invaluable foundation upon which to base 

 further investigations. 



E. G. Hudson 

 Massachusetts Institute of Technology 



SCIENTIFIC JOUBNALS AND ARTICLES 



The April number (Vol. 16, No. 2) of the 

 Transactions of the American Mathematical 

 Society contains the following papers: 



L. E. Dickson : " Quartic curves modulo 2.'' 



W. A. Hurwitz: "Mixed linear integral 

 equations of the first order." 



W. B. Eite : " Prime power groups in which 

 every commutator of prime order is invari- 

 ant." 



W. A. Manning : " On the order of primi- 

 tive groups, II." 



J. W. Alexander, II.: "A proof of the in- 

 varianee of certain constants of analysis 

 situs." 



A. B. Coble: "Point sets and allied Cre- 

 mona groups (part I.)." 



C. T. Sullivan : " Scroll directrix curves." 



The April number (Vol. 21, No. 7) of the 

 Bulletin of the American Mathematical So- 

 ciety contains : " The role of the point-set 

 theory in geometry and dynamics," by E. B. 

 Van Vleck; "An enumeration of integral 

 algebraic polynomials," by A. B. Erizell; 

 " Mr. Paaswell's appeal to producing mathe- 

 maticians," by 0. N. Haskins; Eeview of 

 Volterra's Legons sur les Eonctions des 

 Lignes, by G. A. Bliss ; " Shorter Notices " : 

 Lehmer's List of Prime Numbers from 1 to 

 10,006,721, by L. E. Dickson; Whitford's The 

 PeU Equation, by T. M. Putnam; Liebmann 

 and Engel's Die Beriihrungstransforma- 

 tionen: Geschiehte und Invariantentheorie, 

 by T. H. GronwaU; Pasch's Veranderliche 



