Makers of Electricity

by Brother Potamian; James J. Walsh

Coulomb did not stop here, however, but proceeded to apply his laws to various other phenomena. He proved that electricity distributes itself entirely over the surface of a body without penetrating the mass of the conductor, and he showed by calculation that this result was a necessary consequence of the law of repulsion.

A list of the papers which he published on electricity and magnetism, the titles of which, with French accuracy of expression, furnish an excellent idea of their contents, shows the thoroughly progressive and scientific spirit of the man, and how well he proceeded from the known to the less known, always widening the bounds of knowledge. Suffice it to say here that the observations of Coulomb were not only original, but that they concerned some of the most difficult questions in electricity, and that he was clearing the ground for others in such a way as to make future work and quantitative measurements in electricity reliable and comparatively easy. It is because of this pioneer work that Coulomb deserves so much praise. It was not long before Coulomb's observations were confirmed by others, and then the beginnings of the modern development of electricity became manifest, owing not a little to the researches and inventions, the genius and ingenuity of this French military engineer.

Some phases of electrical development attributed to others really belong to Coulomb. A typical example of this detraction from his merit is the attribution to Biot of the solution of the problem of the complete discharge of an electrified sphere by means of two hollow hemispheres. This experiment is fully described by Coulomb, and he even emphasizes the fact that the external discharging bodies need not necessarily be of the same shape as the charged sphere. Some of what Coulomb accepted as principles in electricity have proved in the course of time, not to be the realities that he thought them; but the progress that has led to such contradictions of his opinions has been mainly rendered possible by his own discoveries. The fable of the eagle stricken by the arrow containing some of its own feathers, is so old that one might think that, when the progress of a science due to a scientist brings men beyond the position he occupied, they would not blame him for backwardness. This is, however, one of the curious critical methods in the history of science that has most frequently to be deprecated by the historian who is tracing origins and developments.

Coulomb's papers, with the exception of his memoir on "Problems in Statics Applied to Architecture," his "Researches on the Methods of executing Works under Water without the Necessity of Pumping," his "Theory of Simple Machines," and his researches "On Windmills," which form separate monographs, were all published together in a single volume by the French Physical Society in 1884.[21]

This volume contains, besides his investigations on the best way of making magnetic needles, his theoretic and experimental investigations on the force of torsion and on the elasticity of metallic threads, which were undertaken in order to enable him to make his electric torsion-balance something more than mere guess-work. All the other papers are concerned directly with electricity or magnetism, and show how actively, nearly a hundred and twenty-five years ago, a great mind was engaged with problems in electricity which we are apt to consider as belonging more properly to our own time. The list of papers published in these memoirs, arranged in chronological order, gives a good idea of the development of electrical science in Coulomb's own mind. There is a logical as well as a chronological order to be observed in them.

In 1785, when he was just approaching his fiftieth year, there were three subjects with regard to which Coulomb's experimental observations enabled him to set down some definite principles. The first of these was the construction and use of an electric balance, founded on the property which wires have of exhibiting a torque proportional to the angle of torsion. The second was the determination of the laws, according to which the magnetic and electric "fluids," as Coulomb and investigators in electricity called them at that time, act both as regards repulsion and attraction. The third was the determination of the quantity of electricity which an insulated body loses in a given time from contact with air more or less moist.

In 1786, he published a paper in which he demonstrated what he considered the principal properties of the electric fluid. These are, that this fluid does not spread itself on a substance by any chemical affinity or any elective attraction, but that it distributes itself over various bodies that are placed in contact, entirely in accordance with their shape; and also that in electrical conductors, the charge is limited to the surface of the conductor and does not penetrate to any appreciable depth.

In 1787, his only paper was on the manner in which the electrical fluid divides itself between two conducting bodies placed in contact, and on the distribution of this fluid over the different parts of the surface of these bodies. He continued his investigations into this subject in 1788, and also succeeded in determining the density of the electricity at different points on the surface of conducting bodies.

In 1789, he began to work more particularly on magnetism. His first paper on the subject was published that year. Unfortunately, as we have said, the Revolution interrupted his scientific investigations at this point, and for the next eleven years we have nothing from his pen. As a nobleman, he was compelled to leave Paris, and this not only put him out of touch with scientific work generally, but deprived him of the opportunities of using such apparatus as was necessary to carry on his experiments. That he acted prudently in leaving Paris, the careers of other scientists amply prove. Lavoisier continued to carry on his chemical investigations during the stormy times of the Revolution, but his stay in the capital eventually cost him his life. Abbé Haüy, the father of crystallography,[22] who, because of his contributions to the science of pyro-electricity, is of special interest to us, continued to work at his crystals throughout even the Reign of Terror. When thrown into prison, he asked and obtained permission to have his crystals with him. His friends saved him from Lavoisier's fate, but not without an effort, as his life was seriously endangered.

It is easy to understand, however, that a member of the nobility like Coulomb, whose life had been spent in military affairs, should not be able to devote himself seriously to scientific matters while his country was in such a turmoil.