Page:Joseph Story, Commentaries on the Constitution of the United States (1st ed, 1833, vol II).djvu/222

 214 that the provision will command universal assent, as soon as it is mentioned. It has grown into a general practice for the vice president to vacate the senatorial chair a short time before the termination of each session, in order to enable the senate to choose a president pro tempore, who might already be in office, if the vice president in the recess should be called to the chair of state. The practice is founded in wisdom and sound policy, as it immediately provides for an exigency, which may well be expected to occur at any time; and prevents the choice from being influenced by temporary excitements or intrigues, arising from the actual existence of a vacancy. As it is useful in peace to provide for war; so it is likewise useful in times of profound tranquility to provide for political agitations, which may disturb the public harmony.

§ 740. The next clause of the third section of the first article respects the subject of impeachment. It is as follows: The senate shall have the sole power to try all impeachments. When sitting for that purpose, they shall be on oath or affirmation. When the president of the United States is tried, the chief justice shall preside. And no person shall be convicted without the concurrence of two thirds of the members present.

§ 741. Upon the subject of impeachments something has already been said, in treating of that branch of the constitution, which delegates to the house of representatives the sole power of impeachment. Upon the propriety of delegating the power it is unnecessary to enlarge. But the next inquiry naturally presented is, by what tribunal shall an impeachment be tried? It is obviously incorrect in theory, and against