He returned as a teacher to Oxford, and a touching record of his devotion to those whom he taught remains in the story of John of London, a boy of fifteen, whose ability raised him above the general level of his pupils.

"When he came to me as a poor boy," says Bacon in recommending him to the Pope, "I caused him to be nurtured and instructed for the love of God, especially since for aptitude and innocence I have never found so towardly a youth.

Five or six years ago I caused him to be taught in languages, mathematics, and optics, and I have gratuitously instructed him with my own lips since the time that I received your mandate.

There is no one at Paris who knows so much of the root of philosophy, though he has not produced the branches, flowers, and fruit because of his youth, and because he has had no experience in teaching.

But he has the means of surpassing all the Latins if he live to grow old and goes on as he has begun." The pride with which he refers to his system of instruction was justified by the wide extension which he gave to scientific teaching in Oxford.