ANTICIPATION OF THE QUADRANT ELECTROMETER THE PORTABLE ELECTROMETER, AND THE ABSOLUTE ELECTROMETER

THOMSON, WILLIAM.

On the Mathematical Theory of Electricity in Equilibrium, On the Elementary Laws of Statical Electricity.

Cambridge, Macmillan and Co., 1846. 8vo. Bound with the original front wrapper in contemporary half calf with black and red title labels to spine with gilt lettering. In "The Cambridge and Dublin Mathematical Journal", Vol. I [1], (Being Vol. V [5], of the Cambridge Mathematical Journal), 1846. Bookplate pasted on to pasted down front free end-paper and library code written in hand to lower part of spine. Library cards in the back. A fine and clean copy. Pp. 75-96. [Entire volume: IV, 288, VIII pp.].

First English translation (and first translation in general) with 'considerable additions' (as stated on p. 75) of Thomson's highly influential paper in which he for the very first time occupies himself with - and anticipates the invention of - the quadrant electrometer, the portable electrometer, and the absolute electrometer.

"When resident in Paris he published in Lionville's Journal a paper [first publication of the present], in which he examined the experiments and deductions of Sir. W. Snow-Harris. This investigator had made an experimental examination of the fundamental laws of Coulomb. Thomson showed by pointing out the defects of Harris' electrometer that the results, instead of disproving these laws, actually confirmed them, so far as they went, from this examination dates Thomson's interest in electrometers, which led to the invention of the quadrant electrometer, the portable electrometer, and the absolute electrometer. " (Lectures on Ten British Physicists of the Nineteenth Century, P. 57).

"Thomson's extensive contact with Liouville led him to think more deeply about electrical theory. Liouville had heard of Faraday's work in electrostatics, or at least of the aspects in which Faraday claimed to have found that electrical induction occurs in "curved lines." The conception seemed to conflict with the action-at-a-distance approach, and Liouville asked Thomson to write a paper clarifying the differences between Faraday on the one hand and Coulomb and Poisson on the other. This request prompted Thomson to bring together ideas he had been turning over in his mind during the previous three years.
From Thomson's new point of view, both the French approach to electrical theory and that of Faraday should consist only of sets of mathematical propositions about the "distribution of electricity" on conducting bodies. Of Coulomb, who had never written like Poisson of the "thickness" of the electrical layer, Thomson said that he had "expressed his theory in such a manner that it can only be attacked in the way of proving his experimental results to be inaccurate." He did not, therefore, believe that Coulomb's approach would stand or fall with the fate of the electrical fluid.

Of course, it may be wondered how Thomson could have employed the phrase "distribution of electricity" without believing that some hypothetical entity is implicated. He did not think so, however. Instead, by 1845 he was drawing a distinction between a "physical hypothesis" and an elementary mathematical law." By a physical hypothesis he meant an assumption concerning the physical existence of an unobservable entity like the electrical fluid or Faraday's contiguous dielectric particles. By an elementary mathematical law he meant a statement that can be directly applied in experiments because its referents are phenomenal entities and mathematical propositions about them. For example, when it is a question of the "distribution of electricity" a phrase that might appear in an "elementary mathematical law," the actual subject concerns the effects produced when a proof-plane is applied to a point of an electrified conductor. The measure of those effects is the twist given to the torsion-bearing thread of an electrometer. Coulomb's laws, therefore, and also those aspects of Poisson's mathematical development of them that do not depend upon the conception of electricity as a physical fluid, were thus actually concise, mathematical laws applicable to the results of such experiments. They were not hypotheses concerning the nature of electricity." (DSB)

Order-nr.: 47439