He was proud of having voted twice for Abraham Lincoln. What he thought
of John Brown, at the time of the Harper's Ferry raid, is uncertain; but
many years later, when one of his friends published a small book in
vindication of Brown against the attack of Lincoln's two secretaries, he
wrote to him:

"I congratulate you on the success of your statement, which I have read
with very great interest. John Brown was like a star and still shines in
the firmament. We could not have done without him."

He considered Governor Andrew's approbation of John Brown as more
important than anything that would be written about him in the future.

He did not trouble himself much in regard to Lincoln's second election,
for he saw that it was a foregone conclusion; but after Andrew Johnson's
treachery in 1866, he felt there was a need of unusual exertion. When the
November elections arrived, he told his classes: "Next Tuesday I shall
have to serve my country and there will be no recitations." When Tuesday
came we found him on the sidewalk distributing Republican ballots and
soliciting votes; and there he remained until the polls closed in the
afternoon. He had little patience with educated men who neglected their
political duties. "Why are you discouraged?" he would ask. "Times will
change. Remember the Free-soil movement!" He attended caucuses as
regularly as the meetings of the faculty, and served as a delegate to a
number of conventions. More than once he aroused the good citizens of
Cambridge to the danger of insidious plots by low demagogues against the
public welfare. The poet Longfellow took notice of this and spoke of him
as an invaluable man.