Otto had untiring perseverance and relentless energy.
The whole march was a running fight between untiring horse-archers and steady infantry.
On this he supported a growing family and gave himself to untiring study.
Little is known of the nature of his occupations during the next two years, except that he was untiring in his efforts to procure first the recall, and afterwards the impeachment of his hitherto triumphant adversary.
He was untiring in literary work, and, though this consisted very largely of occasional papers, lectures, articles in reviews, addresses, and sermons, it included a third volume of his History of the Jewish Church, a volume on the Church of Scotland, another of Addresses and Sermons preached in America, and another on Christian Institutions (1881).