 Hamilton was born on 22 March 1686 to James Hamilton and his wife Elizabeth Reading.His elder brother Robert was baptized on 12 July 1687 but died shortly afterwards, making James the heir apparent, with the style of "Lord Paisley", when his father succeeded as 6th Earl of Abercorn in 1701.A scientist, Hamilton became a Fellow of the Royal Society on 10 November 1715, and published "Calculations and Tables on the Attractive Power of Lodestones", a book on magnetism, in 1729.