master at common law

from Bouvier's Law Dictionary, Revised 6th Ed (1856)
MASTER AT COMMON LAW, Eng. law. An officer of the superior courts of law, 
who has authority for taking affidavits sworn in court, and administering a 
variety of oaths; and also empowered to compute principal and interest on 
bills of exchange and other engagements, on which suit has been brought; he 
has also the power of an examiner of witnesses going abroad, and the like. 
    

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