If on such examination as aforesaid the agent of either party be unable to answer any material question relating to the case which the Collector is of opinion that the party whom he represents ought to answer, and is likely to be able to answer if interrogated in person, the Collector may postpone the hearing of the case to a future day, and direct that the party whose agent may have been unable to answer as aforesaid shall attend in person on such day; and if the party so directed to attend shall fail to appear in person on the day appointed, the Collector may pass judgment as in case of default or make such other orders as he may deem proper in the circumstances of the case.