He was a member of the Connecticut commission on prisons, of the National
Prison Association, and a vice-president of the New York Association for
Prison Reform. A strong advocate of the doctrine of the indeterminate
sentence, he had little patience with many of the judicial outgivings on
that subject. To him they seemed opinions inherited, not formed, and in
most cases were nothing more than the result of prejudice working upon
ignorance. This particular question was one which he purposed to make the
subject of his address as president of the Social Science Association, at
its annual meeting in 1901. He never lived to complete what he had in
mind.

During his later years the rigor of the Northern winter had been too
severe for Warner's health. He had accordingly found it advisable to
spend as much of this season as he could in warmer regions. He visited at
various times parts of the South, Mexico, and California. He passed the
winter of 1892-93 at Florence; but he found the air of the valley of the
Arno no perceptible improvement upon that of the valley of the
Connecticut. In truth, neither disease nor death entertains a prejudice
against any particular locality. This fact he was to learn by personal
experience. In the spring of 1899, while at New Orleans, he was stricken
by pneumonia which nearly brought him to the grave. He recovered, but it
is probable that the strength of his system was permanently impaired, and
with it his power of resisting disease. Still his condition was not such
as to prevent him from going on with various projects he had been
contemplating or from forming new ones. The first distinct warning of the
approaching end was the facial paralysis which suddenly attacked him in
April, 1900, while on a visit to Norfolk, Va. Yet even from that he
seemed to be apparently on the full road to recovery during the following
summer.