The Voltameter
                       Hampden-Sydney College                                           St. Patrick's College, Maynooth, Ireland

   The voltameter is used to measure the electric current by weighing it. The original observation is due to the Italian physicist Carlo Matteucci, who observed in 1835 that in an electroplating system the mass of metal plated onto the cathode is proportional to the current. I once devised an undergraduate experiment on various ways to measure current in which a voltameter was connected in series with a Tangent Galvanometer , a well-calibrated Weston meter and a hefty power supply. In the early days of direct power distribution in Lower Manhattan (1882), Thomas A. Edison installed voltameters in subscribers' premises; the meter reader then "weighed" the current used at the constant DC EMF. The National Museum of Science and Technology of Canada in Ottawa has one of these meters in its collection.

   The Hampden-Sydney apparatus is by Ducretet et Lejune of Paris, and the Maynooth apparatus by F. E. Becker & Co. of London.

   Here is the genuine article: a voltameter by Edison at Case Western Reserve University in Cleveland.

   The electroplating cell is at the lower left-hand corner. Inside can be seen the copper electrodes. At the top is a dropping resistor made of wire folded in the same pattern as the symbol for the resistor. The cover closes to keep inquiring fingers away,

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