A man who discovers one of the most remarkable facts in modern science, namely, that in every atom and molecule there are definite and equal quantities of positive and negative electricity, and that the forces between these electricities are by far the largest known forces which keep together the components of chemical structures, cannot, if he has the imagination of a discoverer, refrain from asking the question: “What is matter?” The reader of Faraday’s “Experimental Researches in Electricity” rejoices whenever Faraday, the poet and prophet, asks an apparently speculative question of this kind, because he knows that he will be thrilled by the poetical fancy which dictates Faraday’s answer. Faraday’s new facts and principles revealed by experiment are steeped in the honey of his fancy; they are rich food made delicious by the flavor of his poetical imagination, even when that flavor leaves the ordinary mortal guessing as to its exact meaning. Two other questions Faraday often approached in these researches; they may be stated as follows: What is electricity? and, What is magnetism? He discovered that motion of magnetism produces electrical forces in a manner similar to that in which, according to Oerstedt’s discovery, motion of electricity produces magnetic forces. This remarkable reciprocal relation between electricity and magnetism stirs up the imagination, and makes it eager to look behind the curtain which separates the region of the revealed truth from that which is still unrevealed. It was undoubtedly this eagerness of the explorer which encouraged Faraday to approach the questions, What is electricity? and, What is magnetism? Faraday never gave a final answer to these questions, but his magnificent efforts to find this answer gave birth to new ideas which are the foundation of our modern electromagnetic view of physical forces. One of the great pleasures of my life has been the contemplation of the gradual unfolding of this new view; and if in the course of this simple narrative I succeed in describing some of its beauties, I shall consider that this narrative was not written in vain.