In 1687, Newton's method of fluxions was first published, twenty years after its invention, and then because the friends of Leibnitz, the author of the "Differential Calculus," claimed priority of discovery. The quarrel aroused the scientific world, embittered the silent mathematician, and impaired his health. In 1689, when he was forty-seven, he was chosen member of parliament, and represented Cambridge University in the House of Commons for thirteen months. He took no active part in the debates, but was of course respected for his wonderful mind. This same year, his beloved mother died. Anxiously he had watched through whole nights by her bedside, seeking in all ways to keep her from leaving him alone in the world. He was now nearly fifty. His life had been laborious, with an insufficient income. His friends, John Locke among the number, tried to obtain various positions for him, but failed. They recommended him for provost of King's College, but the position could not be obtained because he had not taken priest's orders. Seemingly unappreciated, worn with his incessant brain work, his appetite failing, and unable to sleep, with neither mother nor wife to comfort him, the sensitive organization of the great man became overstrained, and mind and body were unfitted for work. It is stated that his ill health was in part consequent upon the burning of some manuscripts on optics, by a lighted candle on the table among his papers. When he was fifty-three, the long hard road of poverty turned into a highway of plenty, through the influence of a friend. Charles Montague, an associate of Newton at the university and also in parliament, though nineteen years his junior,--intellectual affinities are uninfluenced by age,--had been made Commissioner of the Treasury, then Privy Councillor, then Chancellor of the Exchequer, and later still, Baron of Halifax. Lord Halifax appointed Newton to be Warden of the Mint, and then Master, with an income of between six thousand and seven thousand five hundred dollars annually, which position he held for the remainder of his life. His home in London, where he kept six servants, with his brilliant niece, Miss Catherine Barton, for his companion, became a place of rest and comfort to the tired philosopher. Lord Halifax was a great admirer of Newton's niece, Miss Catherine Barton, to whom he left, at his death, a beautiful home and twenty-five thousand dollars, "as a token of the sincere love, affection, and esteem I have long had for her person, and as a small recompense for the pleasure and happiness I have had in her conversation."