premise: the <mask> of a calico-printing machine, which is a knife to remove superfluous coloring matter; the <mask>, or auxiliary engine, called also donkey engine.
hypothesis: the best context for <mask> here is An academical title, originally meaning a man so well versed in his department as to be qualified to teach it.  Hence: One who has taken the highest degree conferred by a university or college, or has received a diploma of the highest degree; . Such diplomas may confer an honorary title only.; but not Any mechanical contrivance intended to remedy a difficulty or serve some purpose in an exigency.