Gerbert, returning into Gaul, became a public professor in the schools, and had as brother philosophers and companions of his studies, Constantine, abbat of the monastery of St. Maximin, near Orleans, to whom he addressed the Rules of the Abacus;[206] and Ethelbald bishop, as they say, of Winteburg, who himself gave proof of ability, in a letter which he wrote to Gerbert, on a question concerning the diameter in Macrobius,[207] and in some other points. He had as pupils, of exquisite talents and noble origin, Robert, son of Hugh surnamed Capet; and Otho, son of the emperor Otho. Robert, afterwards king of France, made a suitable return to his master, and appointed him archbishop of Rheims. In that church are still extant, as proofs of his science, a clock constructed on mechanical principles: and an hydraulic organ, in which the air escaping in a surprising manner, by the force of heated water, fills the cavity of the instrument, and the brazen pipes emit modulated tones through the multifarious apertures. The king himself, too, was well skilled in sacred music, and in this and many other respects, a liberal benefactor to the church: moreover, he composed that beautiful sequence, “The grace of the Holy Spirit be with us;” and the response, “He hath joined together Judah and Jerusalem;” together with more, which I should have pleasure in relating, were it not irksome to others to hear. Otho, emperor of Italy after his father, made Gerbert archbishop of Ravenna, and finally Roman pontiff. He followed up his fortune so successfully by the assistance of the devil, that he left nothing unexecuted which he had once conceived. The treasures formerly buried by the inhabitants, he discovered by the art of necromancy, and removing the rubbish, applied to his own lusts. Thus viciously disposed are the wicked towards God, and thus they abuse his patience, though he had rather that they repent than perish. At last, he found where his master would stop, and as the proverb says, “in the same manner as one crow picks out another crow’s eyes,” while endeavouring to oppose his attempts with art like his own.