<covering letter>

Upminster near Rumford
in Essex 18. Iul. –33

Hond Sr

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

Hond Sr

Your humble servt.

Wm Derham.

<cover sheet (1)>

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

<cover sheet (2)>

To Ioh: Conduit Esqr

<1>

Upminster 18 Iul: 1733.

Hond Sr

According to your desire, I here send you some matters relating to my excellent Friend Sr Is: Newton: wch 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 wth the Colick, yt I was not able to dispatch any considerable business.

I had the Honr & Happiness of Sr 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 wch he hath given the learned World abundant Proof in his <2> Works: in wch he hath shewed his Acumen & Penetration to be equal, if not superior, to yt of Archimedes, Euclid, & other the greatest Wits of former Ages.

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

The first is the Controversy wch Sr Isaac had wth Mr. Leibnitz. Which affair was transacted in the Royal Society whilst I had the Honr to be one of the Council of thereof, & produced some Original Letters yt I found among the Papers of Rich. Townley Esqr (now in my hands) wch plainly demonstrate Sr Isaac's just Title to wt he claims. Which Letters being (as far as <3> relates to this Controversy) published in the Coercium Epistolicum, I shall give no account of: only I think fit to cite, in his own words yt wch 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. Coerc. Epist. p. 29.

When Sr Is: & 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 yt time, revived his his thoughts of these matters, and <4> then he brought them to more perfection, & Counicated them to Dr Barrow, at yt time of the same College, who approving of them, acquainted Mr Collins & other wth them. Thus far Sr Isaac.

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

How Mr Leibnitz came to be informed of Sr Isaac's Method, & afterwards to dress it up with different Terms, & claim it as his own, Sr Is– always spake wth great modesty, with relation to himself, & great honour & regard to the excellent Parts and Capacity of Mr. Leibnitz. He thought it <5> probable yt 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 yt 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, Sr Is. left to the judgment of others.

The other thing wch I said was claimed, was by Dr Hook, & was no lesse a matter than Sr Isaac's Doctrine of the Mundane Systeme. This happened to come into our discours, as Dr Hook and I were discoursing \talking/ about Mr Huygens's celebrated Watch, & the Doctor's Inventions in Watchwork. At <6> which time the Dr took occasion to tell me, yt he had discovered the reciprocal Gravitation of the Planets &c, long before Sr Is: Newton, & complained to me of the injury Sr Is: had done him in robbing him of the Invention. This I thought my self bound, by the Rules of Friendship, to acquaint Sr Is: with. To wch he (wth greater warmth & peevishness than was usual in him) gave me this Answer, That he believed Dr Hook could not perform yt wch 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 (wch are now <7> in my hands) I perceive yt this matter was controverted, & Sr Is: teized about the year 1686. In a Letter of Sr Is: 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 of to their Distances from the Sun 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 Lr of this same date, Sr Is: says he wrote a Lr of Thanks to Hugenius for the 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 yt Lr, and thence take the Notion of comparing ye 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 Lr of Iul. 27. 1686. Sr Isaac speaking of a Lr of his, part of wch, about Colours, was published in Phil: Trans: Nr 96. saith, It is evident from wt I is said there, yt I was at yt 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 {illeg} Distances from the Center they move about: An instance of wch 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 wch Gravity decreased, he had not then experimentally verified, yt is, He knew not how to gather it from Phænomena, & therefore recoends it to the prosecution of others. Thus much I find in the Papers remaining in {the} my hands: but more is in some of the Dr's Papers, wch I delivered up some time since to the R. Society.

The next Remark I shall make shall be of a somewhat out of the way Proof of God, wch Sr Isaac mentioned in some

<10>

These Controversies wth Leibnitz, Hooke, & Linus, & others about Colours, made Sr Is: 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 he imagined, by comprehending his Demonstrations, would concurr wth him in his Theory.

The next Remark I shall make shall be a peculiar sort of Proof of God, wch Sr Is: mentioned in some discourse wch he & I had soon after I published my Astro-Theology. He said there were 3 things in the Motions of the Heavenly Bodies, yt 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 wth 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 Sr Is: 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, Sr. He told me, If the Block-Tin is put into the Crucible to be melted with the Copper, yt the greater part will 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, yt it should be stirred two or three times wth the Spatula, & suddainly poured into the Mold: & yt the cooler & thicker the Melted Metal is, whi|e|n run into the Mold, so much the better it is, than when too hot & thin.

The last thing, Sr, yt I shall trouble you with, shall be a Passage relating to the Coynage of the Copper-money some years agoe, wch pleased me much, as setting forth the Integrity of my Friend, Sr Is. 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, Sr Is: told me, was from the numerous Petitions yt were presented then; in most of wch some person or other of Quality was concerned. Amongst others he told me, yt an Agent of one <13> had made him an Offer of above 6000 li. Wch Sr Is: refusing on account of its being a Bribe; the Agent said, he saw no dishonesty in the acceptance of the Offer & yt Sr Is: understood not his own Interest. To wch Sr Is: replied yt he knew well enough wt was his Duty, & yt no Bribes should corrupt him. The Agent then told him yt he came from a great Dutchesse, & pleaded her Quality & Interest. To wch Sr Is: roughly answered, I desire you to tell the Lady, yt 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, Sr, I have given you an Account, as far as my Memory reaches, of the most material passages yt occur <14> red in my Conversation wth Sr Is: Newton. There were multitudes of lesser matters, yt 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; my Intent & I leave it to you to omit, or insert, & in a word, to make wt use you please of them; my Intent in sending them to you being not only to shew my Veneration of the Memory of Sr Is. Newton, but also the Regard I have to your Request, & yt I am with great Respect

Hond Sr

Your humble servt

Wm Derham.

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Professor Rob Iliffe
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