[5] His 1759 paper "An Experimental Enquiry Concerning the Natural Powers of Water and Wind to Turn Mills and Other Machines Depending on Circular Motion"[6] addressed the relationship between pressure and velocity for objects moving in air (Smeaton noted that the table doing so was actually contributed by "my friend Mr Rouse" "an ingenious gentleman of Harborough, Leicestershire" and calculated on the basis of Rouse's experiments), and his concepts were subsequently developed to devise the 'Smeaton Coefficient'.

[citation needed] Over the period 1759–1782 he performed a series of further experiments and measurements on water wheels that led him to support and champion the vis viva theory of German Gottfried Leibniz, an early formulation of conservation of energy.

This led him into conflict with members of the academic establishment who rejected Leibniz's theory, believing it inconsistent with Sir Isaac Newton's conservation of momentum.

[12] He pioneered the use of 'hydraulic lime' (a form of mortar that will set under water) and developed a technique involving dovetailed blocks of granite in the building of the lighthouse.

[13] In 2020 a Cornish granite bust of Smeaton by Philip Chatfield, commissioned by The Box, Plymouth and funded by Trinity House, was installed in the tower's lantern chamber before its reopening.

[14] Deciding that he wanted to focus on the lucrative field of civil engineering, he commenced an extensive series of commissions, including: Smeaton is considered to be the first expert witness to appear in an English court.

He also improved Thomas Newcomen's atmospheric engine, erecting one at Chacewater mine, Wheal Busy, in Cornwall in 1775 which was both highly efficient and the most powerful at the time.

[25] Smeaton died after suffering a stroke while walking in the garden of his family home at Austhorpe, and was buried in the parish church at Whitkirk, West Yorkshire.

When the upper section of Smeaton's lighthouse (which included the lantern, store and living and watch room) was about to be removed, it was suggested that some of it be brought to Whitkirk and set up as a memorial to him.

The pioneering constant of proportionality describing pressure varying inversely as the square of the velocity when applied to objects moving in air was named Smeaton's coefficient in his honour.