Dare one believe that in electricity the soul of nature had been discovered? This was the question which at that time stirred the hearts of very many in Europe. Doctors had already sought to arouse new vitality in their patients by the use of strong electric shocks; attempts had even been made to bring the dead back to life by such means. . In a time like ours, when we are primarily concerned with the practical application of scientific discoveries, we are mostly accustomed to regard such flights of thought from a past age as nothing but the unessential accompaniment of youthful, immature science, and to smile at them accordingly as historical curiosities. This is a mistake, for we then overlook how within them was hidden an inkling of the truth, however wrongly conceived at the time, and we ignore the role which such apparently fantastic hopes have played in connexion with the entry of electricity into human civilization. (Nor are such hopes confined to the eighteenth century; as we shall see, the same impulse urged Crookes a hundred years later to that decisive discovery which was to usher in the latest phase in the history of science, a phase in which the investigating human spirit has been led to that boundary of the physical-material world where the transition takes place from inert matter into freely working energy.)