to such a proficiency in mathematics, that he was introduced to Sir Isaac Newton, and visited him at Cambridge in the month of November 1692. Though only in the 28th year of his age, his health was precarious, and he seems to have consulted Newton on the subject of his spiritual as well as of his bodily condition. On his return from Cambridge, he caught a severe cold, which affected his lungs, and gave him great alarm. In communicating to Sir Isaac an account of his symptoms, he says, "I thank God that my soul is extremely quiet, in which you have had the chief hand;" and fearing that his illness would prove fatal, he expresses the "wish that his eldest brother, a man of an extraordinary integrity, should succeed him in his friendship." Sir Isaac answered this letter in course of post, making inquiries about his brother, and telling Facio that he remembered him in his prayers. In his reply, Facio gave him his most humble thanks, both for his prayers and his kindness,--requested him thus to remember him as long as he lived, and assured him that he always remembered him in a similar manner.1
1 Nicolas Facio de Duillier, an eminent mathematician, was born at Basle on the 16th February 1664. In 1684 and 1685 he became acquainted with Count Fenil, a Piedmontese, who, having incurred the displeasure of the Duke of Savoy, took refuge in France, where he became captain of a troop of horse. Having quarrelled one day with the commanding officer of his regiment, when drawn up on parade, the Count shot him dead, and, being well mounted, escaped from his pursuers. He fled to Alsace, where he took refuge in the house of Mr. Facio's maternal grandfather; but, in order to assist him more effectually, he was sent to the house of Facio's father, who lived at Duillier. When walking alone with young Facio, the Count told him that he had offered to M. De Louvois to seize the Prince of Orange, and deliver him into the hands of the King; and he showed him the letter of M. Louvois, offering him the King's pardon, approving of the plan, and enclosing an order for money. The Prince of Orange was in the habit of taking a drive on the sands at Scheveling, a village three miles from the Hague, and the Count proposed, with the aid of ten or twelve men, to land in a light ship with Dutch colours, and carry off the Prince to Dunkirk. The scheme was ripe for execution in 1686; but Facio, aware of the Count's design to take the life of his son, felt it his duty to thwart him in the commission of the two crimes which he had in view. He had become acquainted with Dr. Burnet at Geneva, and knowing that he was going to Holland to visit the Prince of Orange, he acquainted the doctor with the Count's scheme, and agreed to accompany him to Holland with the view of explaining it to the Prince. The scheme was accordingly communicated to the Prince and Princess, and, though
