The Galvanoscope
   We are accustomed to the word galvanometer, which indicates the strength of an electric current. The Galvanoscope is an earlier instrument, which shows the presence of the current and gives only a rough indication of its magnitude 

  The basic galvanoscope has only a single turn of wire to set up the magnetic field which turns the magnetic needle. It can be made more sensitive by increasing the number of turns of wire in the loop surrounding the needle. This was first done (in quite different ways) by J. S. C. Schweigger (1779-1857) in 1820 and J. C. Poggendorf (1796-1877) in 1821. Schweigger's method was to wind several turns of copper wire around the compass case. The multiple-turn coil was termed a multiplier because it multiplied the effect of the single turn on the needle. 

   This galvanoscope, at Washington and Lee University, was made by Benjamin Pike, Jr. of New York, and is listed at $3.50 in the 1856 second volume of Pike's catalogue. Note that it is listed by Pike as a galvanometer. There is a similar instrument at Colby College.

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