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WHAT IS ELECTRICITY?

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CHAPTER I.

THE STANDPOINT OF PHYSICISTS IN REGARD TO THE

QUESTION, WHAT IS ELECTRICITY?"

THE question, "What is electricity?" is often asked as if a short and lucid answer could be given which a liberally educated person, could comprehend. In order to understand the grounds upon which a natural philosopher bases his attempts to answer this question one must consider the entire field of activity in which we find ourselves a field which we shall see, is now believed to be due to the electrical energy of the sun. The subject of physics can be said to be the study of the 'transformations of energy, and it is the object of this treatise to describe in a popular ananner how a great intellectual movement, which is now going on silently and steadily, constantly pushing back the limit of our ignorance and occasionally lifting its veil, has taken the place of unsystematic investigation and sterile philosophic vagaries.

Indeed, the characteristic of physical science to-day is its reliance upon patient observation and the study of the transformation of electricity into light and heat or the transformation of heat into electricity. A well

trained physicist listens with as much intolerance to the speculations of a philosopher on the origin of force as Moltke would have listened to the philosophical faculty of the University of Berlin on the origin of war.

The great modern intellectual movement in physical science resides in the abandonment of mere speculation, and the substitution for it of the study of detail and the investigation of the economy of Nature in the transformations of the store of energy which has been vouchsafed to the world. Every university in the world now has its systematic laboratories; and the methods of patient investigation which characterize the laboratory study of science are slowly creeping into the study of other subjects, notably that of law, and are destined, we believe, to be adopted in all subjects.

Lord Salisbury, in an address before the British Association for the Advancement of Science at Oxford, 1894, said: "Science in the universities for many generations bore a signification different from that which belongs to it in this assembly. It represented the knowledge which alone in the Middle Ages was thought worthy of the name of science. It was the knowledge gained not by external observation, but by mere reflection. The student's microscope was turned inward upon the recesses of his own brain, and when the supply of facts and realities failed, as it very speedily did, the scientific imagination was not wanting to furnish to successive generations an interminable series of conflicting speculations.”

The chief characteristic of this marked intellectual method, the most noteworthy movement which scientific education has seen, is the accurate study of the transformations of energy; for we perceive that there

is much to occupy the investigator in this subject and that constant work is repaid by results, whereas philosophical speculations upon what force is and what electricity is gives us no vantage ground over the metaphysicians.

Agnosticism in physical science is a hopeful creed when it is enlivened by a quick imagination, which is employed by the laboratory worker to suggest clues to follow in his study of the transformations of energy.

There is no tendency to restrain the imagination in this attitude of scientific agnosticism. The physicist of to-day has his ethers and his atoms just as the ancient Greek and Roman philosophers had theirs, and he pictures to himself invisible motions far more subtle than entered the imagination of Aristotle or Democritus. The natural philosopher of to-day, however, differs in this essential respect from the ancient philosopher : he measures. If his heat measures do not agree with his hypotheses of vortical or atomic motions, he rejects his attractive hypotheses instead of hugging them.

In my attempt, therefore, to give in a popular manner the speculations of physicists upon the question, "What is electricity?" we must carefully bear in mind the standpoint of investigators and the way in which they hold their hypotheses. However attractive the hypotheses, they are ruthlessly abandoned as soon as the touchstone, the measurement of the heat equivalent of the motion, is not satisfied by the hypotheses. It is not often that one finds an intelligent appreciation of this attitude of holding hypotheses in suspense which is characteristic of the best minds in science of to-day, and indeed the task set for the physicists is not

fully comprehended. They are a small body of men to whom the world looks especially for exact information. By means of patient measurement in the great field of the transformations of energy they have been able to supply the world with the most exact, if not perfectly exact, information which it now possesses. Since the subject of this treatise is a popular presentation of what I regard as the real subject of physics—the transformations of energy-and of the greatest generalization in that subject (Maxwell's Theory of Electro-magnetic Origin of Light and Heat), I can not do better than to quote his words in regard to the attitude of mind and mental characteristics of the order of men whose speculations we are about to study:

"With respect to the 'material sciences,' they appear to me to be the appointed road to all scientific truth, whether metaphysical, mental, or social. The knowledge which exists on these subjects derives a great part of its value from ideas suggested by analogies from the material sciences, and the remaining part, though valuable and important to mankind, is not scientific, but aphoristic. The chief philosophical value of physics is that it gives the mind something distinct to lay hold of, which, if you don't, Nature at once tells you you are wrong. Now, every stage of this conquest of truth leaves a more or less presentable trace on the memory, so that materials are furnished here more than anywhere else for the investigation of the great question, 'How does knowledge come?'

"I have observed that the practical cultivators of science (e. g., Sir J. Herschel, Faraday, Ampère, Oersted, Newton, Young,), although differing excessively in turn of mind, have all a distinctness and a freedom from the tyranny of words in dealing with questions of order,

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