An evill imped wing to flie withall

In the section on Roger Ascham, in A History of Classical Scholarship, v.II, p. 235, J.E. Sandys relates Ascham's thoughts on the value of translations: In opposing the opinion of the bishop, who said, we have no nede now of the Greeke tong, when all things be translated into Latin, Ascham urges that, even the best translation is ... but an evill imped wing to flie withall, or a hevie stompe leg of wood to go withall.