The current required for it is generated by dynamos driven from the axles of the coaches.
Being a bad conductor of electricity it is of value as an insulator, and the smooth flexible sheets are much used in the construction of armatures of dynamos and in other electrical machinery.
About 1879 dynamos began to be introduced into metallurgical practice, and from that date onwards numerous schemes for utilizing this cheaper source of energy were brought before theublic. The first electrical method worthy lectrical P y reduction.
Minor industries are represented by workshops for the production of surgical, musical and geodetic instruments; of telephone and telegraph accessories; dynamos, sewing-machines, bicycles and automobiles.
Following the nomenclature usual in connexion with dynamos we may speak of the conductors which carry the initial charges as the field plates, and of the moving conductors on which are induced the charges which are subsequently added to those on the field plates, as the carriers.
Gramme dynamos were then soon made on the self-exciting principle.
Meanwhile the early continuous current dynamos devised by Gramme, Siemens and others had been vastly improved in scientific principle and practical construction by the labours of Siemens, J.
Deep, the turbines being coupled by long shafts with 5000 H.P. alternating, current dynamos on the surface.
Stimulated and assisted by improvements in the construction of large dynamos and increased knowledge concerning the control of powerful electric currents.