(William), an excellent mathematician and astronomer, was born at Dublin in 1666, and admitted into the university of that city; which when he left, he carried with him a testimonial drawn up in an uncommon form, and in the strongest terms, signifying the high opinion conceived of his genius, the probity of his manners, and the remarkable progress he had made in letters. In 1675, he entered in the middle-temple, where he spent three years in the study of the laws of his country; but the bent of his genius lay strongly toward mathematics and philosophical studies; and even at the university he conceived a dislike to scholastic learning, and fell into the methods of Lord Bacon. Returning to Ireland in June 1678, he shortly after married Lucy the daughter of Sir William Domville the king's attorney-general. Being matter of an easy fortune, he continued to indulge himself in prosecuting such branches of natural and experimental philosophy as were most agreeable to his fancy; wherein astronomy having the greatest share, he began, about 1681, a literary correspondence with Flamsteed the king's astronomer, which he kept up for several years. In 1683, he formed a design of erecting a philosophical society at Dublin, in imitation

(Samuel), son of the former, was born at Chester in July 1684; and educated with great care by his father, according to the plan laid down by Locke upon that subject. When his father died, he fell under the management of his uncle, Dr Thomas Molyneux, an excellent scholar and physician at Dublin, and also an intimate friend of Mr Locke; who executed his trust so well, that Mr Molyneux became afterwards a most polite and accomplished gentleman, and was made secretary to his late majesty when he was prince of Wales. Astronomy being his favourite study, as it had been his father's, he projected many schemes for the advancement of it, and was particularly employed in the years 1723, 1724, and 1725, in perfecting the method of making telescopes; one of which, of his own making, he had presented to John V., king of Portugal. In the midst of these thoughts, being appointed a commissioner of the admiralty, he became so engaged in public affairs, that he had not leisure to pursue these enquiries any farther; and gave his papers to Dr Robert Smith, professor of astronomy at Cambridge, whom he invited to make use of his house and apparatus of instruments, in order to finish what he had left imperfect. Mr Molyneux dying soon after, Dr Smith lost the opportunity; yet, supplying what was wanting from Mr Huygens and others, he published the whole in his "Complete Treatise of Optics."