"Early in 1717 he returned to London, and composed three treatises, which were presented to the Royal Society, and published in the 30th volume of the Transactions. About this time his intense application had impaired his health to a considerable degree; and he was under the necessity of repairing, for relaxation and relief, to Aix-la-Chapelle. Having likewise a desire of directing his attention to subjects moral and religious speculation, he resigned his office of secretary to the Royal Society in 1718. After this he applied to subjects of a very different kind. Among his papers were found detached parts of a Treatise on the Jewish Sacrifices, and a dissertation of considerable length on the Lawfulness of eating Blood. He did not, however, wholly neglect his former subjects of study, but employed his leisure hours in combining science and art; with this view he revised and improved his treatise on Linear Perspective."