The Collaborative International Dictionary of English v.0.48:

Beaumontague \Beau`mon"ta*gue\, n.
   A cement used in making joints, filling cracks, etc. For
   iron, the principal constituents are iron borings and sal
   ammoniac; for wood, white lead or litharge, whiting, and
   linseed oil.
   [Webster 1913 Suppl.]