In 1402 he routed the forces of the Mortimers at Bryn Glas near Knighton in Maesyfed, where he captured Sir Edmund Mortimer, the uncle and guardian of the legitimate heir to the English throne, the young earl of March.
His views on the function of grammar were summarized in a paper on The Spiritual Rights of Minute Research delivered at Bryn Mawr on the 16th of June 1895.
The rebel achieved his greatest success in June 1402, when he surprised and routed the whole levy of the marcher lords at Bryn Glas, between Pilleth and Knighton, capturing (among many other prisoners) Sir Edmund Mortimer, the uncle and guardian of the young earl of March, whom all malcontents regarded as the rightful monarch of England.
He was associate professor of history and political economy at Bryn Mawr in1885-1888and at Wesleyan University in 1888-1890; professor of jurisprudence and political economy at Princeton in 1890-1895, of jurisprudence in 1895-1897, and subsequently of jurisprudence and politics; and in 1902 he became president of Princeton University, being the first layman to hold that office.
In 1881, was an instructor at Columbia in 188'- 1885, and professor at Bryn Mawr in 1885-1895, and became professor of Sanskrit and comparative philology in Yale University in 1895.