§ 421. Proceedings thereon. If an objection to the sufficiency of the impeachment be not sustained by a majority of the members of the court who heard the argument, the defendant must forthwith answer the articles of impeachment. If he plead guilty, or refuse to plead, the court must render judgment of conviction against him. If he deny the matters charged the court must, at such time as it may appoint, proceed to try the impeachment, and may adjourn the trial from time to time until concluded.