<covering letter>

Upminster near Rumford
in Essex 18. Iul. –33

Honoured Sir

I have (after an hindrance by the colick) drawn up my Remarks on Sir Isaac Newton, as you desired, which being too bulky for a Post Letter, I have this day sent them to Mr Innys's in Saint Paul's Church-yard, to be left till you send or call for them. I am with great respect

Honoured Sir

Your humble servant

Wm Derham.

<cover sheet (1)>

To Iohn Conduit Esquire
at his House in Great
George Street Hannover
Square       London.

<cover sheet (2)>

To Ioh: Conduit Esquire


Upminster 18 Iul: 1733.

Honoured Sir

According to your desire, I here send you some matters relating to my excellent Friend Sir Isaac Newton: which you should have had sooner, but I have not been long in this place, where my Memorials are; & have ever since I came been so afflicted with the Colick, that I was not able to dispatch any considerable business.

I had the Honour & Happiness of Sir Isaac's Acquaintance about 30 years. And by our frequent Conversation (for the most part about Philosophical matters) had opportunites of discerning his great Genius, & admirable Parts Of which he hath given the learned World abundant Proof in his <2> Works: in which he hath shewed his Acumen & Penetration to be equal, if not superior, to that of Archimedes, Euclid, & other the greatest Wits of former Ages.

One great sign of which, may be the Ambition which some of the greatest Genij of Sir Isaac's time, had, of robbing him of some of his Inventions. Of which I shall instance in two, becaus I had some concern in them.

The first is the Controversy which Sir Isaac had with Mr. Leibnitz. Which affair was transacted in the Royal Society whilst I had the Honour to be one of the Council thereof, & produced some Original Letters that I found among the Papers of Richard Townley Esquire (now in my hands) which plainly demonstrate Sir Isaac's just Title to what he claims. Which Letters being (as far as <3> relates to this Controversy) published in the Commercium Epistolicum, I shall give no account of: only I think fit to cite, in his own words that which Mr Collins writes to Mr Strode, viz. Mr Newton & Mr Gregory intend to write of this Method in Latin: but Mr Gregory will not anticipate Mr Newton, the first Inventor thereof Vid. Commercium Epistolicum p. 29.

When Sir Isaac & I discoursed about these matters, he gave me this short History of them, viz. That when he was a Iunior at the University, he had thoughts of these things, but brought them to no perfection, by reason he was forced to leave the University in the Plague-year 1665 & 1666. But at his return to Cambridge, Mercator's Logarithmotechia, & what Dr Wallis published about that time, revived his his thoughts of these matters, and <4> then he brought them to more perfection, & Communicated them to Dr Barrow, at that time of the same College, who , acquainted Mr Collins & other with them. Thus far Sir Isaac.

Mr Collins (a man born to promote Mathematicks) I find was so taken with Sir Isaac's Discovery, that he wrote to divers persons about it in 1669, 1670, &c, as appears by his Lettters in my hands.

How Mr Leibnitz came to be informed of Sir Isaac's Method, & afterwards to dress it up with different Terms, & claim it as his own, Sir Isaac always spake with great modesty, with relation to himself, & great honour & regard to the excellent Parts and Capacity of Mr. Leibnitz. He thought it <5> probable that when Mr Leibnitz was in England in the years 1673 & 1676, he might get information of a matter talked of, in his own way, among the Mathematicians, or that his Countryman Mr Oldenburgh might give him information of it But how so great a Genius as Mr Leibnitz came to dresse it up in different colours, & publish it as his own, Sir Isaac left to the judgment of others.

The other thing which I said was claimed, was by Dr Hook, & was no lesse a matter than Sir Isaac's Doctrine of the Mundane Systeme. This happened to come into our discours, as Dr Hook and I were talking about Mr Huygens's celebrated Watch, & the Doctor's Inventions in Watchwork. At <6> which time the Doctor took occasion to tell me, that he had discovered the reciprocal Gravitation of the Planets &c, long before Sir Isaac Newton, & complained to me of the injury Sir Isaac had done him in robbing him of the Invention. This I thought my self bound, by the Rules of Friendship, to acquaint Sir Isaac with. To which he (with greater warmth & peevishness than was usual in him) gave me this Answer, That he believed Dr Hook could not perform that which he pretended to: let him give Demonstrations of it: I know he hath not Geometry enough to do it. I confess I was surprized at this Answer, knowing Dr Hook to be a very considerable man. But by Letters I find among Dr Hooks Papers (which are now <7> in my hands) I perceive that this matter was controverted, & Sir Isaac teized about the year 1686. In a Letter of Sir Sir to Dr Halley of Iun. 20. 1686, he says In one of my Papers written above 15 years agoe, the Proportion of the Forces of the Planets from the Sun reciprocally duplicate to their Distances from him, is exprest: & the Proportion of our Gravity to the Moon's Conatus recedendi a centro terræ is calculated, though not accurately ennough. And in another Letter of this same date, Sir Isaac says he wrote a Letter of Thanks to Hugenius for his Present of his Horologium Oscillatorium, & directed it to Mr Oldenburgh, who used to keep the Originals, & his Papers coming into Mr Hook's hands, he might <8> have the curiosity to look into that Letter, and thence take the Notion of comparing the Forces of the Planets arising from their ciruclar motion; & so what he wrote to me afterwards about the Ratio of Gravity, might be nothing but the Pursuit of my own Garden. And in another Letter of Iul. 27. 1686. Sir Isaac speaking of a Letter of his, part of which, about Colours, was published in Philosophical Transactions Nr 96. saith, It is evident from what is said there, that I was at that time versed in the Theory of the Forces arising from Circular Motions, & had an eye upon the Forces of the Planets, knowing how to compare them by the Proportions of their Periodical Revolutions Distances from the Center they move about: An instance of which you have <9> here in the comparison of the Forces of the Moon arising from her menstrual Motion about the Earth, and annual about the Sun. So then in this Theory I am plainly before Mr Hook. For he about a year after, in his Attempt to prove the Motion of the Earth, declared expresly that the Degrees by which Gravity decreased, he had not then experimentally verified, that is, He knew not how to gather it from Phænomena, & therefore recommends it to the prosecution of others. Thus much I find in the Papers remaining in my hands: but more is in some of the Doctor's Papers, which I delivered up some time since to the Royal Society.


These Controversies with Leibnitz, Hooke, & Linus, & others about Colours, made Sir Isaac very uneasy; who abhorred all Contests, accounting Peace a substantial Good. And for this reason, namely to avoid being baited by little smatterers in Mathematicks, he told me, he designedly made his Principia abstruse; but yet so as to be understood by able Mathematicians, who imagined, by comprehending his Demonstrations, would concurr with him in his Theory.

The next Remark I shall make shall be a peculiar sort of Proof of God, which Sir Isaac mentioned in some discourse which he & I had soon after I published my Astro-Theology. He said there were 3 things in the Motions of the Heavenly Bodies, that were plain Eviden <11> ces of Omnipotence & wise Counsel: 1. That the Motion imprest upon these Globes was Lateral, or in a Direction perpendicular to their Radij, not along them or parallel with them. 2. That the motions of them tend the same way. 3 That their Orbits have all the same, or nearly the same Inclination.

As Sir Isaac Newton was well skilled in Chymistry, & particularly had made divers trials on the Fusion of Metals for Reflecting Telescopes, so I think some of his Observations on this subject worth your Cognizance, Sir. He told me, If the Block-Tin is put into the Crucible to be melted with the Copper, that the greater part thereof will be evaporated; & therefore ought not to be put in untill the Copper is melted. Also if the Tin is too hot, & boyls, it makes the Metal porous. Therefore he advised, <12> when the Tin is put in to the melted Copper, and is it self melted, that it should be stirred two or three times with the Spatula, & suddainly poured into the Mold: & that the cooler & thicker the Melted Metal is, when run into the Mold, so much the better it is, than when too hot & thin.

The last thing, Sir, that I shall trouble you with, shall be a Passage relating to the Coynage of the Copper-money some years agoe, which pleased me much, as setting forth the Integrity of my Friend, Sir Isaac. The occasion of our Discourse was, The great inconveniences which many underwent by the Delay of the Coynage of this sort of Money. The occasion of which Delay, Sir Isaac told me, was from the numerous Petitions that were presented then; in most of which some person or other of Quality was concerned. Amongst others he told me, that an Agent of one <13> had made him an Offer of above 6000 pounds. Which Sir Isaac refusing on account of its being a Bribe; the Agent said, he saw no dishonesty in the acceptance of the Offer & that Sir Isaac understood not his own Interest. To which Sir Isaac replied that he knew well enough what was his Duty, & that no Bribes should corrupt him. The Agent then told him that he came from a great Dutchesse, & pleaded her Quality & Interest. To which Sir Isaac roughly answered, I desire you to tell the Lady, that if she was here her self, & had made me the Offer, I would have desired her to go out of my house, & so I desire you, or you shall be turned out. Afterwards he learnt who the Dutchesse was.

Thus, Sir, I have given you an Account, as far as my Memory reaches, of the most material passages that occur <14> red in my Conversation with Sir Isaac Newton. There were multitudes of lesser matters, that it is scarce worth while to trouble you with. And whether these may be of any use to the kind Design you mentioned to me, you are the best Iudge of; & I leave it to you to omit, or insert, & in a word, to make what use you please of them; my Intent in sending them to you being not only to shew my Veneration of the Memory of Sir Isaac Newton, but also the Regard I have to your Request, & that I am with great Respect

Honoured Sir

Your humble servant

Wm Derham.

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Professor Rob Iliffe
Director, AHRC Newton Papers Project

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