Oersted's Piezeometer
     The name of the Piezeometer comes from the Greek words for pressure and measure, and it is used for measuring the compressibility of liquids. This instrument was invented by Hans Christian Oersted (1777-1851), and consists of a very heavy glass-walled tube sealed at both ends. At the top is a funnel to allow the apparatus to be filled completely with water, and a screw and piston for applying pressure to the water. 
   The inner apparatus has been lost. This consisted of a glass tube containing the liquid to be tested; to the top of the tube was attached a capillary tube which turned downward and had a slug of mercury in it. There was also a separate mercury manometer with an open bottom. As the screw and piston increased the pressure inside the water and the liquid, the movement of the slug of mercury showed the volume change of the test liquid, and the manometer showed the pressure. 
    The example at the left is in the collection of Transylvania University, and was bought from Deluil of Paris in July 1839 for 65 francs. The buyer was Dr. Robert Peter of the Transylvania medical school, who had been sent to Europe to buy apparatus.

   To the right is a similar piece of apparatus in the Garland Collection of Classical Physics Apparatus at Vanderbilt University.

   On the left is a piezeometer at Glasgow University in Scotland.

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