ELECTRICITY. The study of electricity to-day compre hends a vast range of phenomena, in all of which we are brought back ultimately to the fundamental conceptions of electric charge and of electric and magnetic fields. These conceptions are at present ultimates, not explained in terms of others. In the past there have been various attempts to explain them in terms of electric fluids and aethers having the properties of material bodies known to us by the study of mechanics. To-day, however, we find that the phenomena of electricity cannot be so explained, and the tendency is to explain all other phenomena in terms of elec tricity, taken as a fundamental thing. The question "What is electricity?" is therefore essentially unanswerable, if by it is sought an explanation of the nature of electricity in terms of material bodies. Electricity is a name which we give the assumed source of to certain manifestations of force and energy. What is the nature of these manifestations, what are the properties of electricity, will be described in the present article. Only in this sense can we say what electricity is.
The phenomena of static electricity produced by friction were known to the ancients, who were acquainted also with the shock giving properties of the torpedo fish. The discoveries of the electric effects of heat and of chemical action, current electricity and electro-magnetism, however, were not made until after the century A.D., and the study of ionization is a development of the i9th and 2oth centuries.