644 INDEX OF SUBJECTS. 



PAGE 



Two Equal Masses of Opposite Signs 125 



Electrical Moment ' 127 



Principle of Images 128 



Induction in a Medium consisting of Two Dielectrics separated by a Plane . 130 



Three Dielectrics separated by Parallel Planes 131 



Two Equal Masses of Opposite Signs infinitely near each other . . . .134 



Induction on an Infinitely Small Body 139 



.Polarized Sphere. Layers of Gliding 139 



Conducting Sphere in a Uniform Field 142 



Uninsulated Conducting Sphere in a Uniform Field 145 



Dielectric Sphere in a Uniform Field 146 



Concentric Spherical Layers in a Uniform Field 148 



Poisson's Hypothesis of the Constitution of Dielectrics 151 



Two Unequal Masses of Opposite Signs 154 



Electrification of a Sphere under the Influence of a Point 159 



Image of any Given System 162 



Reciprocal Action of Two Spheres 163 



Motion of Small Bodies in the Electrical Field 166 



Direction of a Dielectric Needle in a Variable Field 169 



Action of a Field on a Conducting Needle 173 



CHAPTER VIIL SOURCES OF ELECTRICITY. 



Volta's Discovery 175 



Electromotive Force of Contact 175 



Volta's Laws. Law of Contact 176 



Law of Successive Contacts 177 



Exception to the Law of Successive Contacts. Electrical Batteries . . .178 



Conclusions relative to the Distance of Atoms 179 



Contact of Dielectrics 181 



Electrification by Friction 182 



Electrical Machines 182 



Essential Parts of Electrical Machines 183 



Limit of the Charge 183 



Yield of Machines 185 



