Because of his inheritance, Molyneux was financially independent. Nonetheless, he held a number of official positions throughout his life. He was appointed
Joint Surveyor General of the King's buildings and works in Ireland in 1684, serving alongside
William Robinson. In 1687 he invented a new type of sundial called a
Sciothericum telescopicum that used a special double
gnomon and a telescope to measure the time of noon to within 15 seconds. He represented
Dublin University in Parliament from 1692 until his death. He had also served as a commissioner of forfeited estates in 1693, resigning a few months later due to ill health. Meanwhile, Molyneux was responsible for a number of publications reflecting his diverse interests. His first book was editing and translating into English the work of René Descartes which was published in London, 1680 as
Six Metaphysical Meditations, Wherein it is Proved that there is a God.... In 1682 Molyneux collaborated with
Roderic O'Flaherty to collect material for
Moses Pitt's
Atlas. In 1685, Pitt's financial crisis lead to cancellation of the project but much valuable early Irish history had been collected. Molyneux struck a friendship with O'Flaherty and assisted when the latter's treatise
Ogygia was published in London. He was active in the proceedings of the society—recording weather data, calculating eclipses and demonstrating instruments and experiments. Molyneux also published several papers in Philosophical Transactions, as well as papers on optics, natural philosophy, and miscellaneous topics. Perhaps his best known scientific work was
Dioptrica Nova, A treatise of dioptricks in two parts, wherein the various effects and appearances of spherick glasses, both convex and concave, single and combined, in telescopes and microscopes, together with their usefulness in many concerns of humane life, are explained, published in London 1692. Following a debate in the English House of Commons, it was resolved that Molyneux's publication was 'of dangerous consequence to the crown and people of England by denying the authority of the king and parliament of England to bind the kingdom and people of Ireland'. Despite condemnation in England, Molyneux was not punished but his work was condemned as seditious and was ceremonially burned at Tyburn by the public hangman. His arguments remained topical in Ireland as constitutional issues arose throughout the eighteenth century, and formed part of Swift's argument in ''
Drapier's Letters. The tract also gained attention in the American colonies as they moved towards independence. Although The Case of Ireland, Stated'' was later associated with independence movements—both in Ireland and America—as one historian points out, 'Molyneux's constitutional arguments can easily be misinterpreted' and he was 'in no sense a separatist'. == Legacy ==