The Collaborative International Dictionary of English v.0.48:

Thermometrograph \Ther`mo*met"ro*graph\, n. [Thermo- + Gr. ?
   measure + -graph.] (Physics)
   An instrument for recording graphically the variations of
   temperature, or the indications of a thermometer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

thermometrograph
    n 1: a thermometer that records temperature variations on a
         graph as a function of time [syn: thermograph,
         thermometrograph]