\Sym`pi*e*som"e*ter\, n. [Gr. ? compression (fr. ?
to press together; sy`n with + ? to press, squeeze) +
-meter.]
A sensitive kind of barometer, in which the pressure of the
atmosphere, acting upon a liquid, as oil, in the lower
portion of the instrument, compresses an elastic gas in the
upper part.
Note: The column of oil of a lower part BC of a glass tube
      compresses hydrogen gas in the upper part AB, and is
      thus measured on the scale pq by the position of a
      surface of the oil in the tube. The scale pq is
      adjustable, and its index must be set to the division
      on the scale rs corresponding to the temperature
      indicated by the termometer t, in order to correct for
      the effects of temperature on the gas. It is sensitive,
      and convenient for use at sea, but inferior in accuracy
      to the mercurial barometer.