JOHN THEOPHILUS, who introduced the practice of reading public lectures in experimental philosophy in the metropolis, and who made several improvements in mechanics, was the son of the Reverend John Desagulliers, a French Protestant refugee, and was born at Rochelle on the 12th of March 1683. His father brought him to England whilst yet an infant, and at a proper age placed him at Christ-Church College, Oxford, where he at length succeeded Dr Keill in reading lectures on experimental philosophy at Hart-Hall, and prosecuted his researches in physics. The Duke of Chandos made Dr Desagulliers his chaplain, and presented him to the living of Whitchurch; and he afterwards became chaplain to Frederick prince of Wales. He read lectures with great success till the time of his death, which happened in the year 1749. He communicated many curious papers, which are printed in the Philosophical Transactions; published a valuable Course of Experimental Philosophy, in 2 vols., 4to; and gave an edition of Gregory's Elements of Optics and Dioptries, with an appendix on reflecting telescopes, 8vo. He was a member of the Royal Society, and also of several foreign academies. If credit may be attached to poetical authority, Desagulliers, at the time of his decease, must have fallen into very necessitous circumstances. Cawthorn laments his fate in these lines:

How poor, neglected, Desagulliers fell! How he who taught two gracious kings to view All Boyle ennobled, and all Bacon knew, Died in a cell, without a friend to save, Without a guinea, and without a grave.