Officers appointed by and attached to the circuit courts of the United States, performing functions partly ministerial and partly judicial. To a certain extent they represent the judge in his ab- sense. In the examination of persons arrested for violations of the laws of the United States they have the powers of committing magistrates. They also take bail, recognizances, affidavits, etc., and hear preliminary proceedings for foreign extradition. In re Com’rs of Circuit Court (0. C.) 05 Fed. 317.