Abstract :
STEPHEN GRAY AND FRANKLIN IT is now two hundred years since Stephen Gray discovered that an electrical charge will move with great rapidity along certain substances called conductors today. The motion of electricity began then to attract the attention of the natural philosopher, and it became the subject of many scientific researches, particularly after Franklin had demonstrated that lightning is a motion of electricity. There is no doubt that many a scientist of Franklin´s time associated with the destructive power of lightning something resembling the destructive power of a projectile; something endowed with an irresistible momentum. But who would have dared to suggest in those days that moving electricity just like moving matter had a momentum? Nobody suspected in those days that the history of the electrical science of the first half of the nineteenth century would be a record of the gradual evolution of this electrical momentum concept. Oersted´s discovery in 1819 of the magnetic field of force accompanying the motion of electricity marks the first step in the progress of that evolution.
