Expansion of Gas Due to Heating
   This is a differential instrument: the slug of water or mercury in the horizontal section of tubing would be pushed in one direction or the other, depending on the rate at which the air in the two bulbs is expanded by electrical heating. Its ancestor is  Kinnersley's Thermometer. The heating is accomplished by thermocouples in the two bulbs; the manufacturer called this a "Peltier Effect Apparatus." The catalogue notes that "a 2-Ampere flow of current for 10 seconds will produce a 10 to 12 mm movement of a water index in the horizontal connecting tube.

   The wooden stand is cut out behind the horizontal tubing, allowing the apparatus to be used with a light source to throw an enlarged image on the screen for the entire class to see.

   

This piece of apparatus at Kenyon College, is listed at $17.50 in the 1936 catalogue of the Chicago Apparatus Company, which used the Milvay Scientific Supplies designation for much of its apparatus.

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