Leeds and Northrup of Philadelphia made a series of "potentiometer indicators" for use with thermocouples for the determination of temperature. The instrument on the left, with a thermocouple still attached, was listed for $120 in the 1940 Central Scientific catalogue. The one on the right is somewhat older. Both are furnished in rugged oak cases for field work. They have a self-contained standard cell. These instruments were given to the Greenslade Collection by Daniel Chaucer.
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