Ladd, Boston, 1887); Werner Luthe, Beitrage zur Logik (Berlin, 1872, 18 77); Members of Johns Hopkins University, Studies in Logic (edited by C. S.
Hazen, Contemporary American opinion of the French Revolution (Johns Hopkins University, Baltimore, 1897).
Johns, Hastings's Dict.
Three years later he was appointed professor of mathematics in the Johns Hopkins University, Baltimore, stipulating for an annual salary of $5000, to be paid in gold.
From 1876 almost until his death he was connected with the Johns Hopkins University, Baltimore, Maryland, being in turn a fellow, an associate in history (1878-1883), an associate professor (1883-1891) and after 1891 professor of American and institutional history.