the same idea as some sentences in the scholium beginning "Deus summus est ens æternum, infinitum, absolute perfectum ;" and it is remarkable that the second paragraph is found only in the third edition of the Principia, which appeared in 1726, the year before Newton's death.

In reviewing the details which we have now given respecting the health and occupations of Newton from the beginning of 1692 to 1694, it is impossible to draw any other conclusion than that he possessed a sound mind, and was perfectly capable of carrying on his mathematical, his physical, and his theological inquiries. His friend and admirer, Mr. Pepys, residing within fifty miles of Cambridge, had never heard of his being attacked with any illness till he inferred it from the letter to himself written in September 1693. Mr. Millington, who lived in the same University, had been equally unacquainted with any such attack, and, after a personal interview with Newton, for the express purpose of ascertaining the state of his health, he assures Mr. Pepys, "that he is very well; that he fears he is under some small degree of melancholy, but that there is no reason to suspect that it hath at all touched his understanding."

During this period of bodily indisposition, his mind, though in a state of nervous irritability, and disturbed by want of rest, was capable of puting forth its highest powers. At the request

tonum incidisse in Phrenitim;' but I think every gentleman who examines this manuscript will be of opinion that he must have thoroughly recovered from his phrenitis before he wrote either the Commentary on the Opinions of the Ancients, or the Sketch of his own Theological and Philosophical Opinions which it contains." An account of this manuscript, by Dr. J. Gregory, has been published in the Edinburgh Transactions for 1829, vol. xii. pp. 64-67.-See Rigaud's Hist. Essay, p. 99.

1This paragraph is as follows:-"Deum esse ens summe perfectum concedunt omnes. Entis autem summe perfecti Idea est ut sit substantia una, simplex, indivisibilis, viva et vivifica, ubique semper necessario existens, summe intelligens omnia, libere volens bona, voluntate efficiens possibilia, effectibus nobilioribus similitudinem propriam quantum fieri potest communicans, omnia in se continens tanquam eorum principium et locus, omnia per presentiam substantialem cernens et regens, et cum rebus omnibus, secundum leges accuratas ut naturæ totius fundamentum et causa constanter co-operans, nisi ubi aliter agere bonum est."

of Dr. Wallis he drew up examples of one of his propositions on the quadrature of curves in second fluxions. He composed, at the desire of Dr. Bentley, his profound and beautiful letters on the existence of the Deity. He was requested by Locke to reconsider his opinions on the subject of innate ideas. Dr. Mill engaged him in profound biblical researches, and we shall presently find him grappling with the difficulties of the lunar theory.

But with all these proofs of a vigorous mind, a diminution of his mental powers has been rashly inferred from the cessation of his great discoveries, and from his unwillingness to enter upon new investigations. The facts, however, here assumed, are as incorrect as the inference which is drawn from them. The ambition of fame is a youthful passion, which is softened, if not subdued, by age. Success diminishes its ardour, and early pre-eminence often extinguishes it. Before the middle period of his life Newton was invested with all the insignia of immortality; but endowed with a native humility of mind, and animated with those hopes which teach us to form a humble estimate of human greatness, he was satisfied with the laurels which he had won, and he sought only to perfect and complete his labours. Although his mind was principally bent on the improvement of the Principia, yet he occasionally diverged into new fields of scientific research-he created, as we shall see, his fine theory of astronomical refractions—he made great improvements on the lunar theory-he solved difficult problems, which had been proposed to try his strength, he wrote a profound letter to Leibnitz,—he made valuable additions to his "Opticks," -he continued his chemical experiments, and he devoted much of his time to profound inquiries in chronology and theological literature.

The powers of his mind were therefore in full requisition; and, when we consider that he was called to the discharge of high official functions which forced him into public life, and compelled him to direct his genius into new channels, we can

scarcely be surprised that he ceased to produce any very original works on abstract science. In the direction of the affairs of the Mint, and of the Royal Society, to which we shall now follow him, he found ample occupation for his time; while the leisure of his declining years was devoted to those exalted studies in which philosophy yields to the supremacy of faith, and hope administers to the aspirations of genius.1

1 Some light has been recently thrown on the illness of Newton by Dr. Dowson of Whitby, who, at a meeting of the Philosophical Society there, on the 3d of January 1856, read a paper "On the supposed Insanity of Sir Isaac Newton," in which he has shown that the malady with which he was afflicted in September 1693 was probably Influenza or Epidemic Catarrhal Fever, which prevailed in England, Ireland, France, Holland, and Flanders in the four last months of 1693. This distemper, which lasted from eight or ten days to a month, was so general, that "few or none escaped from it ;" and it is therefore probable, as Dr. Dowson believes, that Newton's mental disorder was merely the delirium which frequently accompanies a severe attack of Influenza. See Dr. Theophilus Thomson's Annals of Influenza or Epidemic Catarrh in Great Britain, published in 1852 by the Sydenham Society. See also the Philosophical Transactions for 1694, vol. xviii. pp. 105-115.

CHAPTER XVIII.

Newton occupied with the Lunar Theory-His Correspondence with Flamsteed, the Astronomer-Royal-Newton's Letters to Flamsteed, published by Mr. Baily-Controversy which they occasioned-Flamsteed's Letters to Newton discovered recently -Character of Flamsteed, in reference to this Controversy-Of Newton, and of Halley-All of them engaged, with different objects, in studying the Lunar TheoryNewton applies to Flamsteed for Observations on the Moon, and on the Refraction of the Atmosphere, which Flamsteed transmits to him-Analysis of their Correspondence-Flamsteed's bitterness against Halley-Differences between Newton and Flamsteed-Flamsteed's ill health interferes with his supplying Newton with Observations-Newton's impatience and expostulation with Flamsteed-Justification of Flamsteed-Biot ascribes Newton's Letter to Mental Illness-Refutation of this view of the subject--Newton never afflicted with any mental disorder.

WHILE Newton was supposed to be incapable of understanding his Principia, we find him occupied with the difficult and profound subject of the lunar irregularities. He had resumed this inquiry in 1692,1 and it was probably from the intense application of his mental powers which that subject demanded, that he was deprived of his appetite and sleep during that and the subsequent year. When Mr. Machin long afterwards was complimenting him upon his successful treatment of it, Sir Isaac told him that his head had never ached but when he was studying that subject; and Dr. Halley told Conduitt that he often pressed him to complete his theory of the moon, and that he always replied that it made his head ache, and kept him awake so often, that he would think of it no more. On a future occasion, however, he stated to Conduitt, that if he lived till Halley made six years' observations, "he would have another stroke at the moon." "2

1 Rigaud, Hist. Essay, p. 104.

2 Conduitt's Manuscript notes.

66 re

In order to verify the equations which he had deduced from the theory of gravity, accurate observations on the moon were required; and, for the purpose of obtaining them, Newton had arranged, in the month of July 1691, to pay a visit to Flamsteed at the Royal Observatory of Greenwich. Learning, however, that Flamsteed was at that time from home, he postponed his visit, and intimated what had been his intention, in a letter of introduction which David Gregory delivered to the Astronomer-Royal in August 1691.1 During this visit Gregory introduced the subject of the lunar irregularities, and, in a letter to Newton, gives him an account of the conversation which arose on this and other subjects. "Flamsteed," he says, membered you very kindly ;" and, among other things, he said "that he did not believe the irregularity of the moon's motions in summer and winter is of that quantity your system would make it."2 In the letter delivered by Gregory, Newton had advised Flamsteed to publish a catalogue of the correct places of such fixed stars of the first six magnitudes, as had been observed by others, and afterwards, by way of an appendix, those observed by himself alone,-an advice which, from causes perhaps not then known to Newton, struck a discordant key in the mind of Flamsteed. He believed that this advice was suggested by Halley, whom he considered as an enemy, who had misrepresented him to his friends as unwilling to print his observations. He enters, therefore, in a long letter,3 into an explanation of his reasons for not printing his observations, and he concludes the letter with the severest animadversions upon Halley, which it is impossible to justify. "I have no esteem," he says, "of a man who has lost his reputation, both for skill, candour, and ingenuity, by silly tricks, ingratitude, and foolish prate; and that I value not all, or any of the shame of him and his infidel companions; being very well satisfied, that if

1 Dated 10th August 1691, published in Baily's Flamsteed, p. 129.

2 August 27, 1691, unpublished.

3 February 24, 1692. Baily's Flamsteed, pp. 129-133.