The Collaborative International Dictionary of English v.0.48:

Baroscope \Bar"o*scope\ (b[a^]r"[-o]*sk[=o]p), n. [Gr. ba`ros
   weight + -scope: cf. F. baroscope.]
   Any instrument showing the changes in the weight of the
   atmosphere; also, less appropriately, any instrument that
   indicates or foreshadows changes of the weather, as a deep
   vial of liquid holding in suspension some substance which
   rises and falls with atmospheric changes.
   [1913 Webster] Baroscopic