PREFACE. IX 



and Heaviside has been little used. It is easy to lay so much 

 stress on symbolism that the student loses sight of the real sim- 

 plicity of the method. In order, however, to show its extreme 

 utility, particularly in connection with the operator V, the essen- 

 tials of the quaternion notation have been explained in the first 

 chapter. 



As the aim of the book has been to present an introduction 

 to the mathematical theory of electricity, little or no reference 

 has been made to experimental methods in fact it seems that 

 such subjects as standard cells, dynamos, or galvanometers should 

 be treated in a separate work, and I have no desire to add to the 

 large number of such already existing. At the same time it is 

 hoped that the principles involved in the various modes of mea- 

 surement are all herein contained. 



The figures with which the book is illustrated, while but a few 

 of them are new, have in no case been copied from existing 

 figures, but have been, if necessary, recalculated, and in every case 

 redrawn on a large scale and photographed down to the required 

 size. For the amount of labor here involved I am under great 

 obligations to Messrs W. P. Boynton and T. W. Edmondson, 

 fellows of Clark University, who have undertaken the whole 

 matter. As the proof has been read only by the author, it is 

 probable that a certain number of errors have crept in, which it 

 is hoped may be excused. 



In conclusion my aim has been to present a brief, connected 

 treatise embodying the essential points of the theory and suitable 

 for assimilation by the student in a period of time not exceeding 

 a year. To this end I have considered only the usual methods of 

 treating the various subjects, and included enough examples to 

 illustrate their working, and no more. If it be considered that 

 unnecessary matter has been included it may be replied that this 

 may easily be omitted, and that it is safer to include too much 

 than to make unwarrantable assumptions regarding the know- 

 ledge possessed by the student. If the book shall succeed in 



