DESAGULIERS, JOHN THEOPIIILUS, D.D., was born at Rochelle on the 12th of March 1683, and brought,to England while an iufant by his father the Rev. John Desaguliers, a French Protestant refugee, after the revocation of the edict of Nantes. His early educa tion he owed to the instructions of his father, who appears to have been a very respectable scholar and sound divine, and at an early age he was scut to Christchurch, Oxford. In 1702, being then only nineteen, he succeeded Dr. Neil in reading lectures on Experimental Philosophy at Hart Hell ; and he ever afterwards prosecuted his physical researches with great earnestness and success. Upon his marriage in 1712, he settled iu London, where he was the first that introduced the reading of lectures to the public on natural and cape. rimental philosophy. This he did with great and continued reputation to the end of his life, which terminated in 1749, in the sixty-sixth year of his age. The highest personages mere attracted by the novelty of his mode of teschine; and he was several times honoured with reading his lectures before the king and royal family.
In 1714 Desaguliers was elected a Fellow of the Royal Society, of which he preved a valuable member. The Duke of Chandos appointed him his chaplain, and presented him with the living of Edgeware, near his seat at Cannons; and Ile was afterwards made chaplain to the Prince of Wales.
From some causes which are not well understood, Desaguliers appears to have fallen into a state of great destitution ;—we say appear!, for the authority on which the assertion rests has, so fir as know, neither received collateral proof nor denial. He certainly did remove to lodgings over the Piazza in Covent Garden, in which ho continued his lectures; but the lines of the poet Cawthorn are the only authority on which the statement of extreme indigence rests :— " Ilene peon neglected Desaguliers fell How he who taught two gracious kings to view All Boyle ennobled, and all Bacon knew, Died in n cell, without a friend to nave, Without a guinea, and without a grave I" If this statement be true, he must either have been the dupe of others to a great extent, or singularly improvident in his own affairs; as besides his emoluments from his lecturing, he held two church livings.
The separate writings of Dcsaguliers contain an elegant exposition of the more popular portions of experimental philosophy. His minel was more fitted for the popular and the practical than for the pro• founder inquiries into those branches of science; and for the geome trical method of investigation than for the higher and then new calculus which has since so completely changed the whole current of research. His works are—I, 'A Connie of Lectures on Experimental Philosophy,' 2 vols. 4to, 1734. 2, An Edition of Dr. David Gregory's Elemeuts of Catoptrics and Dioptrice, with an A ppeudix on Reflecting Telescopes,' Svo, 1735. This appendix contains some original letters betwi en Sir Isaac Newton and Mr. James Gregory relative to these telescopes, which are worthy of attention. 3, A Translation of the curious, valuable, and little known Treatise on Perspective,' by S'Gravesande, Svo. 4, 'A Translation of S'Omvesande's Natural Philosophy,' 2 vols. 4to, 1747. 5, 'A Translation of Nieuwentyt's Iteligioue Philosopher,' 3 vols. 8vo. Several respectable papers by Desaguliers are inserted in the 'Philosophical Transactions' from 1714 to 1743.