CONTENTS, 



PART I.-GENERAL CONSIDERATIONS. 



HISTORICAL SKETCH 



IMPORTANT DEFINITIONS ......... 4 



Electric current ............... ^ 



Electro-motive force ............... - 



Tension of a current ...... ... ...... 5 



Electrical potential .., ............ 6 



Electrical intensity ......... ... 6 



Electrical resistance ... ... ... ... 7 



Electrical conductivity ...... 8 



Electrodes ... ......"... g 



Polarization ......... ......... g 



Electric Units ......... ...... ... ]0 



WHAT THE ELECTRIC LIGHT IS ... ... '^/.^ " s ,.. 12 



THE VOLTAIC ARC 



PART II.-GENERATORS OF ELECTRIC LIGHT. 



VOLTAIC GENERATORS ... ..,......, ... 2$ 



Groves and Sunset? s batteries '.,, .,v ... 25 



