vi PREFACE 



the various members of the class while engaged with the same 

 general topic carry out the experimental work by alternative 

 methods. 



For the use of those who desire a more detailed discussion of 

 the various methods, references to certain important papers are 

 appended to each chapter. While no attempt had been made 

 to form a bibliography of the subject of electrical measurements 

 it is thought that these references should be of value in directing 

 the students' attention to the original sources of information 

 and thus assisting him to a broad view of this particular part of 

 his professional training. 



The various commercial instruments described in the text have 

 been selected simply as giving good illustrations of the applica- 

 tion of the particular principles under discussion. No attempt 

 has been made to discuss instruments made by different makers 

 which differ merely in minor details. 



The author wishes to thank Professor H. E. Clifford, Gordon 

 McKay Professor of Electrical Engineering at Harvard Univer- 

 sity, for his continued interest in the work and for the many 

 and valuable suggestions which he has made during its 

 preparation. F. A. LAWS. 



MASSACHUSETTS INSTITUTE OF TECHNOLOGY 

 July 5, 1917. 



