The correspondence, which lasted till 1713, was printed, with notes and a synoptical view of Newton's life by Edleston, in 1850, and is of the greatest value to all students of Newton. Six letters on the velocity of effluent water, written by Cotes to Newton in 1710–11, are not printed by Edleston (Cotes Corr.), but are with the Portsmouth correspondence. The edition was not completed till 1713. Newton's various other duties contributed to cause the delay, though his friends were anxious to complete the work more rapidly. Thus (Maccl. Corr. i. 264, 16 March 1712) Saunderson, who succeeded Whiston as Lucasian professor in 1711, wrote: ‘Sir Is. Newton is much more intent on his “Principia” than formerly, and writes almost every post about it, so that we are in great hopes to have it out of him in a very little time.’
In 1714 Newton was one of Bishop Moore's assessors at Bentley's trial (Monk, Life of Bentley, pp. 281–6), and the same year he gave evidence before a committee of the commons on the different methods of finding the longitude at sea (Edleston, Cotes Corr. lxxvi, n. 167). In 1716 Cotes died (ib. lxxi, n. 171). Newton is reported to have said on hearing of his death, ‘If he had lived we might have known something.’
In 1717 and 1718 Newton presented reports to parliament on the state of the coinage. In 1724 he was engaged in preparing the third edition of the ‘Principia,’ which appeared, under the editorship of Pemberton, in 1726. He was laid up with inflammation of the lungs and gout in 1725, but was better after this for some time. However, he overtaxed his strength by presiding at a meeting of the Royal Society on 2 March 1727, and from this he never recovered. He died at Kensington on 20 March, in the eighty-fifth year of his age.
His body lay in state in the Jerusalem Chamber, and was buried in Westminster Abbey on 28 March 1727. A conspicuous monument, bearing a Latin inscription, was erected to his memory in the abbey in 1731. He was succeeded as master of the mint by his nephew by marriage, John Conduitt [q. v.] The family estate at Woolsthorpe went to John Newton, the heir-at-law, the great-grandson of Sir Isaac's uncle.
During the time of his residence in London Newton lived first in Jermyn Street, then for a short time at Chelsea, and afterwards in Haydon Square, Minories, in a house pulled down in 1852. From 1710 until 1727 in a large plain-built brick house (to which he added a small observatory) next Orange Street chapel in St. Martin's Street, Leicester Square. A Society of Arts tablet has been placed upon the front of the house.
At the time of his death there were living three children of his stepbrother, Benjamin Smith; three children of his stepsister, Marie Pilkington; and two daughters of his stepsister, Hannah Barton. These eight grandchildren of his mother became the heirs of his personal property, which amounted to 32,000l., and they erected the monument in Westminster Abbey at a cost of 500l. His stepniece and heiress, Catherine Barton, married in 1717 John Conduitt, and her daughter married John Wallop, viscount Lymington, eldest son of John Wallop, first earl of Portsmouth; she was thus mother of John Wallop, second earl of Portsmouth. Through this marriage a number of Newton's manuscripts passed into the hands of the Earls of Portsmouth at Hurstbourne, and the scientific portion of them was presented to the university of Cambridge by the fifth Earl of Portsmouth in 1888; the rest remain at Hurstbourne. A full catalogue of the mathematical papers by Professors Adams and Stokes was published in 1888 (‘A Catalogue of the Newton MSS.,’ Portsmouth collection).
Professor Adams points out that the manuscripts show that Newton carried his astronomical investigations far further than Laplace supposed. Many theological and historical manuscripts which are in the Portsmouth collection are of no great value; some on chemistry and alchemy are of ‘very little interest in themselves.’ Newton left notes of chemical experiments made between 1678 and 1696. The most interesting relate to alloys.
Some of the papers left by Newton at his death dealing with theological and chronological subjects were afterwards published (Brewster, Life of Newton, vol. ii. chap. xxiii.). Leibnitz in 1710 had attacked Newton's philosophy, and in a letter written to the Princess of Wales in 1715 he made a number of charges against the religious views of the English. George I heard of the attack, and expressed a wish that Newton should reply, and he was thus brought into contact with the princess; in the course of conversation with her, he mentioned a system of ancient chronology composed by him when in Cambridge, and shortly afterwards gave her a copy. The Abbé Conti, under a strict promise of secresy, was allowed to take a copy of it. On his return to France Conti violated his promise and gave it to Freret, who wrote a refutation and then had it published without Newton's permission. Newton had neglected to answer two letters on the subject. The work was printed in 1725, and led to various
