Later life of Isaac Newton
Open-knowledge reference entry
During his residence in London, Isaac Newton had made the acquaintance of John Locke. Locke had taken a very great interest in the new theories of the Principia. He was one of a number of Newton's friends who began to be uneasy and dissatisfied at seeing the most eminent scientific man of his age left to depend upon the meagre remuneration of a college fellowship and a professorship.
1693
During the period 1692–1693 Newton is known to have suffered a breakdown of nervous functioning, or a supposed depression lasting for 18 months, as reported by Huygens. He suffered insomnia and poor digestion, in his letters to friends showing signs of irrationality.
During exhumation the hair from Newton's dead body was found to contain high levels of mercury, remains of desiccated hair were later found to contain four times the lead, arsenic and antimony and fifteen times mercury than in normal range samples. Two hairs contained mercury and separately lead at levels indicating chronic poisoning. Symptoms of mercury poisoning exhibited by Newton were apparently tremor, severe insomnia, delusions of persecution or paranoid ideas, problems with memory, mental confusion, and withdrawal or decline from personal friendships, significant in the period of time, the deterioration of his relations with his protégé Nicolas Fatio de Duillier.
Newton documented the first performed alchemy experiment during 1678, having first obtained furnaces and chemicals in 1669. Experiments with metal included analysis of taste of which there are 108 documented, including mercury: strong, sourish, ungrateful, documented also by the scientist were similar experiments with arsenic, gold and lead.
This brief starts where responsible research should: with the source description of “Later life of Isaac Newton” as open-knowledge reference entry. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the general reference register because the source frames it as open-knowledge reference entry. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Apr 2, 2026. The linked authority identifier is Q6495541. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1693, 1692, 1678 and 1669.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Later life of Isaac Newton”, its source revision and the description used here.
- Expand the search: follow Later life of Isaac Newton primary sources, Later life of Isaac Newton archive and Later research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Later life of Isaac Newton”?
- What terminology or title could unlock a more precise catalogue search?
- Which cited source is closest to the event, object or claim?
Search terms from this dossier
This entry incorporates text from “Later life of Isaac Newton” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.