election, they shall be divided, as equally as may be, into three
classes.[1] The seats of the senators of the first class shall be vacated
at the expiration of the second year; of the second class, at the
expiration of the fourth year; and of the third class, at the expiration
of the sixth year;[2] so that one-third may be chosen every second year;
and if vacancies happen by resignation, or otherwise, during the recess of
the legislature of any state, the executive thereof may make temporary
appointments until the next meeting of the legislature, which shall then
fill such vacancies.[3]_

[1] The object of this division is to secure for the Senate at all times a
large proportion of experienced members. By this arrangement, too, the
Senate becomes a permanent body, ready at any time to convene for the
consideration of treaties, for the trial of impeachments, or for
confirming executive appointments.

[2] Only ten states were represented when, on May 15, 1789, this
classification was first made. (North Carolina and Rhode Island had not
yet ratified the constitution, and New York's senators had not yet
presented their credentials.) The twenty senators had on the preceding day
been grouped by name into three classes, two of seven senators each, and
one of six. By the drawing of three numbered slips of paper, seven fell
into class 1, seven into class 2, and six into class 3, with terms ending
March 3, 1791, 1793, and 1795, respectively. After the classification had
been fixed, the two senators from New York appeared. One was placed, by
lot, in class 3 (thus filling the classes), and then the other, also by
lot, in class 1. The two senators from the next state, North Carolina,
were therefore placed in the unfilled classes 2 and 3. Since 1795, each
class holds for six years, and a senator's term expires with that of his
class.

[3] Senators represent the state, and are elected by the body which acts
for the state,--by the legislature if in session, temporarily by the
governor if it is not.

_Clause 3.--Qualifications_.

_No person shall be a senator, who shall not have attained to the age of
thirty years,[1] and been nine years a citizen of the United States,[2]
and who shall not, when elected, be an inhabitant of that state from which
he shall be chosen.[3]_

[1] This was also the age for eligibility to the Roman Senate. It is five
years more than the requirement for membership in the House.

[2] Two years of citize