At the Royal Society meeting in London on 10 December 1684, Edmond Halley reported that Newton had recently shown him a curious treatise on motion at Cambridge. Newton himself was not present.
Halley said Newton had promised to send the treatise for entry in the Society's register. The meeting asked Halley and Edward Paget to remind him, so that he could secure priority for the work before publication.
What was in it
The work developed mathematical relations between centripetal force and orbital motion: equal areas swept in equal times, the inverse-square force associated with an ellipse's focus, and the period–axis relation now counted among Kepler's laws.
The surviving draft runs to roughly 3,911 Latin words on nine pages, formally structured as four theorems and seven problems. It grew out of Halley's August 1684 visit to Cambridge, where he challenged Newton to demonstrate the orbit produced by an inverse-square central force; Newton supplied a demonstration through Paget in November.
What the register copy did not prove
The tract was sent and entered later, by February 1685. It was not read to the Society on 10 December, and a date written on the later register copy does not prove the copy was physically registered then.
The original manuscript is lost; what survives is a draft and contemporary copies, so even the title De motu corporum in gyrum is not securely that of the lost original. The meeting date is Old Style, corresponding to 20 December 1684 in the Gregorian calendar.
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Traditional date. This date is the conventional one, not one fixed by a contemporary record.
What the sources leave uncertain
The meeting date is an English Old Style/Julian date. It corresponds to 20 December 1684 in the Gregorian calendar.
The original manuscript is lost. What survives is a draft and contemporary copies, including a register-book copy; the title De motu corporum in gyrum is not securely the title of the lost original.
The exact relationship among the November demonstration, the treatise Halley saw in Cambridge and the version later registered has long been debated. The meeting record is nevertheless clear that Halley gave an account of a promised tract rather than reading the tract itself.
The engine's power stroke came from the weight of the atmosphere, not from steam pressure — and the principal evidence for its famous date is an engraving made seven years later.
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Thomas Newcomen and John Calley's team erected an atmospheric pumping engine near Dudley, conventionally dated to 1712 and traditionally identified with Coneygree Coalworks at Tipton, to raise water from a coal mine.
Steam at little more than atmospheric pressure filled an open-topped cylinder. Injected cold water condensed it, producing a partial vacuum, and ordinary atmospheric pressure then pushed the piston down. Chains joined the piston and the mine pump rods to opposite ends of a rocking beam, so the working stroke lifted the rods and the rods' own weight returned the piston.
Why the mines needed it
Flooding limited how deeply coal and metal mines could be worked, and Thomas Savery's earlier pumping system had a suction lift of only about 20 feet, which left it poorly suited to pumping directly from deep workings. The installation demonstrated that a piston-and-beam atmospheric engine could perform practical mine drainage at depths that severely limited Savery's system.
Engines followed in the Midlands and northeastern coalfields. By 1733, according to the ASME and Newcomen Society account, at least 95 had been built in Britain.
Which engine was first
No exact construction or commissioning day is established. The conventional year rests chiefly on Thomas Barney's 1719 engraving, which dates the depicted engine's erection to 1712.
Historians disagree on what counts as first. A 2018 engineering-history study distinguishes earlier experiments, a Stow Heath engine described as the first to draw water, and Coneygree as the first installation to receive broad publicity; another study considers a Wheal Vor engine in Cornwall in 1710 highly likely.
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Date disputed. Sources disagree; the research places it at ~1712.
What the sources leave uncertain
No exact construction or commissioning day is established. The conventional year 1712 rests chiefly on Thomas Barney’s engraving made in 1719, supported by circumstantial documentation.
Historians disagree about what should count as the first engine. A 2018 engineering-history study distinguishes earlier experiments, a Stow Heath engine described as the first to draw water, and Coneygree as the first installation to receive broad publicity. Another scholarly study considers a Wheal Vor engine in Cornwall in 1710 highly likely.
Coneygree is well supported as the site of the traditionally celebrated 1712 'Dudley Castle' engine, but labeling it unconditionally as the first working Newcomen engine suppresses the surviving dispute.
In 1736 Henry Woodfall printed John Colson's English translation of Newton's unpublished Latin treatise as The Method of Fluxions and Infinite Series, and John Nourse sold it in London.
Newton had written the Latin treatise in about 1670–71 and died in 1727. The Latin original itself was not printed until a later collected edition, so English readers got the translation first. Colson supplemented it with commentary on the interpretation and foundations of the fluxional method.
A separate, anonymous book
Also in London that year, an anonymous tract titled An Introduction to the Doctrine of Fluxions defended mathematicians against objections raised in George Berkeley's 1734 attack, The Analyst. Its author was Thomas Bayes, though his name was absent from the original title page. The tract had 50 numbered pages, plus preliminary and advertising leaves.
Bayes discussed fluxions and prime and ultimate ratios in answer to Berkeley. The tract was not a companion volume commissioned for Colson's publication, and no evidence establishes that the two books were released on the same day or as a coordinated project.
What can and cannot be dated
Only the year is securely established for both publications; no common day or month has been verified. Newton's manuscript is variously dated 1670–71 or given as completed in 1671.
The attribution of the anonymous Introduction to Bayes is accepted in bibliographies and in scholarship. Newton's manuscripts and earlier mathematical communications had circulated well before 1736, so this was not the occasion on which anyone first learned of his calculus.
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Date disputed. Sources disagree about when this happened.
What the sources leave uncertain
Only the year 1736 is securely established for both publications; no common day or month has been verified.
Newton’s manuscript is variously dated 1670–71 or completed in 1671.
Attribution of the anonymous Introduction to Bayes is accepted in bibliographies and scholarship, but his name did not appear on the original title page.
The first volume of Linnaeus's tenth edition appeared in Stockholm with a 1758 imprint, published by Lars Salvius under the Latin form Holmiae, and covered the animal kingdom in viii preliminary pages plus 824 numbered ones.
The surviving title page supplies a year, not a day. For nomenclatural purposes the International Code of Zoological Nomenclature arbitrarily deems the work published on 1 January 1758 — a status imposed retrospectively, not announced at the time.
Names that stuck
In this volume Linnaeus consistently applied two-part genus-and-species names across the animal kingdom. Homo sapiens is here, and so is the sea lamprey Petromyzon marinus, named on page 230 and still attributed to Linnaeus, 1758.
The revised classification renamed Quadrupedia as Mammalia, moved whales and dolphins from the fishes into the mammals, and renamed Anthropomorpha as Primates.
What came with the names
Linnaeus divided Homo sapiens into six groupings — ferus, americanus, europaeus, asiaticus, afer and monstrosus — of which only four were geographical varieties, and attached prejudicial physical and behavioural descriptions to them.
The edition ran to two volumes: animals in 1758 and plants on 7 June 1759, with a projected mineral volume never published as part of it. Calling the author Carl von Linné in 1758 is anachronistic; he was ennobled in 1761.
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What the sources leave uncertain
January 1 is explicitly described by the zoological Code as arbitrary. The defensible historical date is therefore 1758; January 1 is a conventional nomenclatural date.
The work's tenth edition was issued in two volumes: Animalia in 1758 and Vegetabilia in 1759. A proposed mineral volume was not published as part of this edition.
At Paris on 10 February 1763, the Duke of Bedford, the Duke of Praslin and the Marquis de Grimaldi signed the definitive peace for Great Britain, France and Spain. Portugal was a contracting party through accession — the treaty expressly acknowledges that Portugal had not signed it.
The terms had been shaped by the preliminary peace concluded at Fontainebleau in November 1762.
What changed hands
France ceded Canada with its dependencies, Cape Breton Island, and the other French islands and coasts in the Gulf and River St Lawrence. It also ceded its possessions on the eastern side of the Mississippi, New Orleans and its island excepted.
Spain ceded Florida; Britain agreed to restore Havana and its other Cuban conquests to Spain, and returned several captured Caribbean islands to France. France kept Saint-Pierre and Miquelon for its fishery, undertaking not to fortify them and to keep a guard of no more than fifty men.
The clauses with caveats
Britain promised Canada's inhabitants freedom of Roman Catholic worship — only so far as British law permitted. Former French subjects had eighteen months after the exchange of ratifications to emigrate and dispose of their property.
The public text kept New Orleans French, though France had secretly ceded the city and Louisiana to Spain in November 1762. Signature fixed the terms rather than the transfers: ratifications were due within a month, and were exchanged on 10 March.
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What the sources leave uncertain
The signature date is well established by the treaty and surviving originals. Physical possession did not change everywhere on February 10; many clauses operated only after the exchange of ratifications.
By Watt's own much later recollection, he entered Glasgow Green through the gate at Charlotte Street on a Sunday afternoon in 1765, thinking about the Newcomen engine. Near the herdsman's house he realized that steam could rush from the working cylinder into an exhausted separate vessel and be condensed there without cooling the cylinder.
Before he reached the Golf-house, he said, he had also worked out how to remove the condensate and air — either through a descending pipe 35 or 36 feet deep with a small pump, or through a larger pump handling both.
Why it mattered
The Newcomen engine condensed steam inside its working cylinder, reheating and cooling the same metal every stroke. The Science Museum puts the heat consumed in reheating the University of Glasgow's Newcomen model at about 80 percent.
A separate condenser let the working cylinder stay hot while condensation happened in a permanently cool vessel. Engines using it later burned about two-thirds less coal.
The date nobody can source
No consulted primary or scholarly source supports 26 May. Reliable institutional accounts say only May 1765, or 1765; Hart's account describes merely a fine Sunday afternoon, so the specific day looks like a calendar reconstruction.
The detailed route and dialogue come from a paper Robert Hart read in 1857, recalling a conversation with Watt held in 1813 or 1814. Watt did follow through: he tested the principle with a small cylinder, condenser pipes and an air pump, and surviving Science Museum models confirm experimental condenser work in 1765.
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Traditional date. Conventionally dated here; the research places it at ~1765-05.
What the sources leave uncertain
No consulted primary or scholarly source independently supports May 26. Reliable institutional accounts say only May 1765 or 1765, and Hart's recollection says merely a fine Sunday afternoon.
The detailed route and dialogue come from Robert Hart's paper read in 1857. Hart was recalling a conversation held in 1813 or 1814—nearly fifty years after the supposed walk and decades after Watt's death.
The insight itself is well supported by Watt's technical work and later accounts, but the precise eureka-scene details should be presented as Watt's remembered story, not a contemporaneous diary entry.
Short of food, losing men and lacking reliable news of Sir Henry Clinton's operations, Burgoyne compromised with his officers on 7 October 1777 and sent a reconnaissance-in-force of more than 1,500 troops southwest to probe the American defenses and forage in two wheatfields.
Gates committed Daniel Morgan's corps and the brigades of Enoch Poor and Ebenezer Learned against the British right, left and center. By about 5 p.m. the Americans had driven Burgoyne's force from the wheatfields, and Simon Fraser was mortally wounded commanding the rearguard.
One redoubt held, the other did not
The British Light Infantry, or Balcarres, Redoubt resisted the American attacks. The Breymann Redoubt on the northwestern flank of Burgoyne's camp was undermanned — fewer than 200 defenders against more than 1,000 American troops — and it fell.
Benedict Arnold was severely wounded in the left leg during that assault, and the redoubt's commander, Heinrich von Breymann, was killed.
Much of the camp abandoned that night
With his northwestern defenses breached, Burgoyne abandoned much of his camp and consolidated his army close to the Hudson River that night.
The National Park Service puts British-led losses at more than 630 against about 150 American. The day produced no surrender: withdrawal toward Saratoga followed, and the capitulation came ten days later.
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What the sources leave uncertain
Casualty figures are estimates and vary among official accounts; the current detailed NPS page gives more than 630 British-led casualties and about 150 American casualties.
Arnold’s exact authority and movements remain historiographically contested. The current NPS account says Gates authorized him to lead a major reinforcement, while older narratives often depict him acting entirely without authorization.
Under articles negotiated with Horatio Gates, Burgoyne's troops marched out on 17 October 1777 with the honors of war and deposited their arms and artillery near the ruins of Fort Hardy, in present-day Schuylerville, New York.
Only two American officers watched them pile their weapons and empty their cartridge boxes at the Field of Grounded Arms. The defeated column afterwards marched between silent lines of American soldiers.
The sword, and the terms
Burgoyne and Gates met on the road near the Dutch Reformed Church, then dined with their staffs. The ceremonial sword presentation came later, while the surrendered army marched past; Gates returned the sword.
The Convention promised Burgoyne's army passage to Great Britain on condition that its members not serve again in North America during the conflict, with Boston assigned as the port of embarkation.
Who actually marched away
The current NPS accounting puts about 6,300 British and German officers and soldiers under the Convention, with roughly 600 women and children accompanying them; the Library of Congress figure of 5,871 counts British regulars and German troops only. Most Canadiens and Loyalists were permitted to return to Canada instead.
Burgoyne had reported 3,500 effective fighting men left, fewer than 2,000 of them British, and three days' provisions on short allowance. By the end of the day his invasion army had been disarmed and had started toward Massachusetts as the Convention Army.
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What the sources leave uncertain
The surrender date is secure. The surviving Convention document is dated October 16, while its final article required mutual signature and exchange the next morning and execution followed on October 17.
Published totals differ because returns count different populations—regular soldiers, officers, Canadians, Loyalists, sailors, camp followers, women and children. The current NPS estimate of about 6,300 British and German officers and soldiers is broader than the Library of Congress figure of 5,871 British regulars and German troops.
Most Canadiens, Loyalists and other Canadian-establishment personnel were permitted to return to Canada; roughly 200 Abenaki and Mohawk allies had already departed. Thus “entire army” can obscure who was actually included in the Convention.
The discovery began in the garden of a working musician's townhouse in Bath, not at a royal observatory — and what Herschel thought he had found was a comet.
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Between 10 and 11 p.m. on 13 March 1781, William Herschel was examining small stars near H Geminorum when one object struck him as visibly larger than the others. He was working from the garden of his home in Bath, England, with a reflecting telescope he had built himself.
The instrument had a 6.2-inch aperture, and it showed him a resolved disc rather than an ordinary point of light. The object was in Gemini, not Taurus — Uranus had been catalogued in Taurus by earlier observers who took it for a star.
Herschel did not conclude that night that he had found a planet. His initial suspicion was that the object was a comet.
Four nights later, the wrong answer
On 17 March the object had changed position, and Herschel treated that as confirmation of a comet. The motion only established that it was not a fixed star; the comet reading was his own inference, and it was wrong.
He reported a supposed comet to the Royal Society. Nevil Maskelyne, the Astronomer Royal, helped circulate and evaluate the observation among other astronomers, and Anders Johan Lexell's calculation of a nearly circular orbit helped establish that the object was a planet rather than a comet.
Georgium Sidus, and how long it lasted
Herschel later proposed the name Georgium Sidus in honour of George III, and subsequently received royal patronage worth £200 a year. Johann Elert Bode proposed Uranus in 1782 to preserve the mythological naming pattern.
Bode's name did not take over at once. Britain's Nautical Almanac retained the Georgian name until 1850.
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What the sources leave uncertain
Calling March 13 the 'discovery of the planet Uranus' is correct retrospectively. Herschel did not know that night that he had found a planet.
Herschel was not yet 'Sir William' in 1781; he was knighted in 1816.
Georgium Sidus was a later proposed planetary name, not the label Herschel gave the object during the first observation.
30 August 1781: twenty-eight sail inside the capes
On 30 August 1781 the Comte de Grasse entered Chesapeake Bay with 28 French ships of the line and anchored in Lynnhaven Roads. He had left Haiti on 5 August by an indirect route meant to keep the British from guessing his destination.
The fleet that sailed comprised 28 ships of the line, seven frigates and two cutters. The Naval History and Heritage Command puts the embarked troops at 3,200; the National Park Service gives 3,000.
The watchers trapped in the bay
De Grasse's arrival caught two British observation frigates inside the Chesapeake and kept them there, so no prompt report of French strength reached the British command.
Samuel Hood had looked into the bay on 25 August, before the French arrived, and had gone on to New York.
Troops ashore, then the British response
De Grasse began landing French troops to reinforce Lafayette's force, which was watching Cornwallis in the Yorktown area. Anchored inside the capes, the fleet now stood between Cornwallis and any Atlantic route for evacuation or reinforcement.
The position did not go unchallenged for long. Thomas Graves and Hood combined their available ships and sailed from New York on 31 August.
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What the sources leave uncertain
The Naval History and Heritage Command explicitly dates the entry and anchoring to August 30. A National Park Service account says the fleet arrived “four days” after Hood’s August 25 visit, which would imply August 29, but supplies no explicit alternative date and appears to contain an arithmetic or wording error.
Official accounts differ slightly over the embarked troop total: the Naval History and Heritage Command gives 3,200, while the National Park Service gives 3,000.
The deputies declared existing taxes legally unauthorised — then ordered officials to go on collecting them anyway, temporarily, so the state would not seize up.
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At the Menus-Plaisirs hall in Versailles on 17 June 1789, the deputies meeting as the Commons voted on Abbé Sieyès's motion to constitute themselves under the name "National Assembly." It carried by 491 votes to 90.
The name itself came from the floor: Jérôme Legrand proposed the wording, and Sieyès revised his motion to take it in.
A claim to speak for the whole country
The motion asserted that the verified deputies present represented at least ninety-six hundredths of the nation. Weeks of failed negotiation over joint verification and voting by head had produced nothing, so the Commons had verified deputies on its own.
The resolution kept a door open. Members of the two privileged orders could still join once their credentials were verified, collectively or individually — and several parish priests had already come across.
Oaths that day, a locked door three days later
Having declared the existing taxes legally unauthorised, the new Assembly ordered their temporary collection to continue and provided for servicing the public debt. Jean-Sylvain Bailly, the secretaries and then the whole chamber took oaths.
On 20 June the deputies found their hall locked and guarded. They moved to a nearby tennis court and swore not to separate before giving France a constitution.
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At Versailles on 26 August 1789, the National Constituent Assembly finished its article-by-article voting on the Declaration of the Rights of Man and of the Citizen. The voting had occupied four sitting dates: 20, 21, 25 and 26 August.
The Assembly had decided on 4 August that its constitution must be preceded by a declaration of rights.
Drafted by committee, then voted article by article
Five deputies — Mirabeau, Démeunier, La Luzerne, Tronchet and Redon — were charged with fusing the numerous submitted projects into a single text, and reported on 17 August. Lafayette and Sieyès had each put forward influential drafts of their own.
What emerged was a composite: a preamble and 17 articles, declaring natural rights, equality before the law, national sovereignty, legal safeguards, and freedoms of opinion and expression.
Adopted is not ratified
Article 17, the last of them, protected property while allowing expropriation for a legally established public necessity, and only with prior just compensation.
The Assembly's adoption was not royal ratification. Louis XVI accepted the Declaration on 5 October, under pressure from the Assembly and from the crowd that had come to Versailles.
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What the sources leave uncertain
The date is secure, but “proclaimed” is imprecise. August 26 marks completion of the Assembly’s adoption; royal acceptance and formal promulgation were later stages.
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