Jim Frysinger wrote in USMA 14435 >Immediately I was struck by the surprising realization that you are >using electrostatic units for at least some of your teaching and >homework assignments. This has stimulated my curiosity and some >questions come to mind. I haven't seen these units in print since I >read the journal articles written by Millikan a century ago regarding >his famous oil drop experiments. In fact, the use of esu's was >superceded so long ago that I cannot find the date on which they were >deprecated. Certainly, they were replaced when the SI was brought into >being forty years ago. I am on two IEEE standards committees (one >jointly with the ASTM) and I cannot recall ever seing those units used >in any of their materials. Nor can I recall their use in any AIP >publications in the last few decades. I have tracked down the history of the SI electric units in "�tude critique du Syst�me m�trique" by Maurice DANLOUX DUMESNILS, published by Gauthier-Villars, 1962. In 1881 at the first Congr�s international des �lectriciens Lord Kelvin proposed the adoption of a "legal" system of units formed by decimal multiples or sub-multiples of the electromagnetic cgs units ohm, volt, amp�re, coulomb and farad. The second Congress, 1889, created the watt, henry and joule. In 1893 the Congress met in Chicago and renamed the "legal" system as the "syst�me internatioinal". In 1891 the American Institute of Electrical Engineers added the weber, gilbert, oersted and gauss. All these units were based on the metre, kilogram and second, and the implied magnetic permeability of space of 1.00... In 1882-1983 Oliver Heaviside showed that the force between magnetic poles should be m1.m2/4�r^2 instead of m1.m2/r^2. On 1901 Giovanni Giorgi proposed a system of "rational" units which involved choosing the amp�re, volt, or ohm as a 4th base unit, and adjusting the magnetic units so that the factor 4� would be eliminated. This also required changing the permeability of space. In 1935 the Commission �lectrotechique Internationale voted in favor of Giorgi's "rational" system. In 1948 the IXe Conf�rence G�n�rale des Poids et Mesures invited the international scientific unions to consider the question of the electromagnetic units. Their unanimous support was for the Giorgi system. So in 1954 the Conf�rence G�n�rale des Poids et Mesures adopted the Giiorgi system, with base units metre, kilogram, second and amp�re as base units. They named the system the "Syst�me Internationale d'Unit�s". SI was not universally accepted. Soem favored the old system. Among the "Giorgians" there were "rationalisers" and "non rationalisers" although they have now practically disappeared. I leave it to the American physicists of this mailing list to decide where to place the physicists of Princeton. Joseph B. Reid 17 Glebe Road West Toronto M5P 1C8 Tel. 416 486-6071
