PREFACE. 



WHILE the electric arc is one of the most common things 

 of modern life, an understanding of it is not common. 

 This is largely due to the difficulty of becoming familiar 

 with the investigations which have been made on this 

 subject. There have indeed been many articles published 

 concerning it, but they are scattered through many pub- 

 lications, and the data given by different experimenters are 

 not consistent with each other, and none of the explanations 

 are entirely satisfactory. 



"The Electric Arc," by Mrs. Hertha Ayrton, gave an 

 account of the experiments which were performed prior to 

 1898, but very little investigation had been made at that 

 time of any arc except the open carbon arc, and none of 

 the explanations based on the ionic theory had been given, 

 so that by far the greater part of what is now known 

 concerning the arc could not then be described. An excel- 

 lent work in German, "Der elektrische Lichtbogen" by 

 Berthold Monash, has more recently appe.ared, but this 

 deals but briefly with the theoretical side and does not 

 meet the requirements of those who would read English 

 rather than German. 



It, therefore, seemed desirable to offer another dis- 

 cussion of the electric arc, giving especial attention to the 

 explanation of the phenomena and to those investigations 

 which have been made since the publication of Mrs. 



