Page:Electricity (1912) Kapp.djvu/38



distinction generally found in textbooks on physics between the so-called "frictional" and "contact" electricity does not imply that there are two different kinds of electricity, but it refers to two different methods of producing electrification of bodies. Besides these two there are other methods, and some of them are of much greater practical importance. Those will be discussed in subsequent chapters; for the present we restrict the discussion to the two methods mentioned above.

The term "frictional electricity" indicates the process by which the electrification of a body is produced. If a stick of sealing-wax is rubbed with a flannel, both these bodies show electrification, but of opposite sign. We agree to call the electricity residing on the sealing-wax negative, and that on the flannel positive. Electricity may also be