Isaac Newton

Newton returns to Cambridge and is elected a Trinity fellow

Newton's 1667 expense notebook records three prisms and four ounces of polishing putty — the shopping list of a researcher back from plague isolation.

Spring 1667, back in Cambridge

Newton returned to Cambridge in spring 1667 after plague-related residence in Lincolnshire and resumed his university life; accounts variously put the definitive return in March or April.

On 1 October he was elected a minor fellow of Trinity College, with eight others — among the year's first fellowship elections, Trinity having held none in 1665 or 1666.

What he brought back, and did not publish

The work he carried back included investigations in infinite series, what became differential and integral calculus, refraction, and the heterogeneity of white light. Much of it had been written during 1665–1666 rather than on any date in 1667.

Nothing was published. His dated October calculus tract stayed private, and Newton Project editors caution that its inscribed 1666 date may have been added later, during the priority struggle with Leibniz.

The things that are not 1667

The first working reflecting telescope belongs to 1668. The theoretical treatment of the speed of sound appeared in Book II of the 1687 Principia, and the paper containing the cooling relation, Scala graduum caloris, was published in 1701.

Newton became Lucasian Professor in 1669, and the Crown's dispensation allowing Lucasian professors to avoid holy orders came in 1675.

Sources

Researched 24 Aug 2026 9 sources not yet audited Date disputed

How this was checked

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Date disputed. Sources disagree about when this happened.

What the sources leave uncertain

The listed item is not a discrete dated event. It conflates work from approximately 1664–1666, Newton’s 1667 return and fellowship, and results first developed or published in later decades.
Newton’s movements around the plague closures are reconstructed from college allowances and later records; sources variously describe his definitive return as March or April 1667.
The Newton Project notes that the date “October 1666” on the early calculus tract may have been added later during the priority controversy, although the work itself belongs to this early period.
“Thermodynamics” is an anachronistic umbrella term here, and the relevant cooling work cannot be securely assigned to 1667.