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John Whitehurst Royal Society (10 April 1713 – 18 February 1788), born in Cheshire, England, was a clockmaker and scientist, and made significant early contributions to geology. He was an influential member of the Lunar Society.
In 1772 - aged 59 years- he invented the "pulsation engine" (not to be mixed up with a Pulser pump), a water-raising device which was the precursor of the hydraulic ram.
In 1778, Whitehurst published his theory on geological strata in An Inquiry into the Original State and Formation of the Earth. He had begun this while living at Derby, originally intending to facilitate the discovery of valuable minerals beneath the Earth's surface. He pursued his researches with so much ardour, that "the exposure he incurred" tended to impair his health.
On 13 May 1779, Whitehurst was elected a fellow of the Royal Society. In 1783, he was sent to examine the Giant's Causeway and the volcanic remains in the north of Ireland, embodying his observations in the second edition of his Inquiry.
About 1784 he contrived a system of ventilation for St. Thomas's Hospital.See Bernan's History and Art of Warming and Ventilation, 1845, ii. 70
In 1786, Whitehurst was elected as a member to the American Philosophical Society.
In 1787, age 74, a year before his death, he published An Attempt towards obtaining invariable Measures of Length, Capacity, and Weight, from the Mensuration of Time (London). Whitehurst wanted to study the shape of the earth by measuring differences in gravitation. For this, he studied heavy pendulums in different locations. He measured the length of the pendulum, the frequency of its oscillation and the length of the path its head was moving. He compared these to theoretical values he calculated assuming the globe is spherical. Starting on the assumption that the length of a second pendulum in the latitude of London was 39.2 inches, he deduced that the length of one oscillating 42 times a minute is 80 inches, while that of one oscillating twice as many times is 20 inches. The difference between these two lengths would therefore be exactly 5 feet. He found upon experiment that the actual difference was only 59.892 inches owing to the real length of the pendulum, oscillating once a second, being 39.125 inches. He obtained rough data, from which the true lengths of pendulums, the spaces through which heavy bodies fall in a given time, and many other particulars relating to the force of gravitation and the true figure of the earth could be deduced.
It has been suggested that Whitehurst is the model for Joseph Wright of Derby's picture of A Philosopher Lecturing on the Orrery in the Derby Museum and Art Gallery.
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