Source : Webster's Revised Unabridged Dictionary (1913)

Claude Lorraine glass \Claude" Lor*raine" glass`\ [Its name is
   supposed to be derived from the similarity of the effects it
   gives to those of a picture by Claude Lorrain (often written
   Lorraine).]
   A slightly convex mirror, commonly of black glass, used as a
   toy for viewing the reflected landscape.