The Collaborative International Dictionary of English v.0.48:

Blowtube \Blow"tube`\, n.
   1. A blowgun. --Tylor.
      [1913 Webster]

   2. A similar instrument, commonly of tin, used by boys for
      discharging paper wads and other light missiles.
      [1913 Webster]

   3. (Glassmaking) A long wrought iron tube, on the end of
      which the workman gathers a quantity of "metal" (melted
      glass), and through which he blows to expand or shape it;
      -- called also blowing tube, and blowpipe.
      [1913 Webster]