the principle of repeating many times, if possible in many different ways, the one thing that it is desired to impress on readers or hearers.) When, in the same year, Duke John Frederick of Hanover, Leibniz s subsequent patron, who was persona gratissima with the French King and Court, visited Mainz, Leibniz hoped for a personal introduction through him to the great monarch, and it was afterwards intended that the same thing should be effected by the Elector of Mainz, to whom Leibniz s scheme had by that time been communicated by Boineburg. In the end, however, it was agreed to send a general statement of the nature of the scheme to Paris beforehand, reserving its details for the present. In February 1672, Boineburg was informed by Pomponne, then French minister for Foreign -Affairs, that the King wished for further explanations from the author of the preliminary memorandum. Thereupon, Leibniz (taking occasion, according to his wont, to combine various scientific projects with his great political design) at once started for Paris, where he arrived in March 1672. In the same month, France and England declared war against the Dutch, and in two months time a great part of the United Provinces had been overrun by the French forces, with King Louis XIV at their head. From the camp at Doesburg Pomponne sent a rather nonchalant message that Holy Wars had gone out of fashion; and it might have been supposed that Leibniz at Paris would have hereupon been satisfied to concentrate his attention upon subjects of common interest between himself and Antoine Arnauld, the inventor of the pendulum, and Christian Huygens, the discoverer of Saturn's ring.
Not so; for, though the Dutch War had not been averted, it seemed by no means certain that its worst apprehended consequences could not still be avoided. It had long been known that there was a great deal of diplomatic tension between the French Government and the Sublime Porte; and, in June, 1672, an open rupture occurred between the two Governments at Adrianople,
