Mr Ray, who had now betaken himself to a more sedentary and studious mode of life, began to suffer severely in his health. His Catalogue of English Plants having become scarce, he was solicited by some friends to improve it for a third edition, which he accordingly did; but a difference arising between him and the booksellers, to whom the copyright belonged, he forthwith resolved to publish it in another form. In the mean time, however, to satisfy his friends, he printed his Fasciculus Stirpium Britannicarum, as a substitute for the Catalogue. In 1690, appeared the Synopsis Methodica Stirpium Britannicarum, which may be considered as the most important work on British plants that has been hitherto written, with the exception of Sir James Smith's English Botany, and its continuation by Dr Hooker. It was farther augmented by him, and reprinted in 1696, together with a description of the Cryptogamic plants, which had hitherto received little attention. Having thus published many important works on natural history, he resolved to compose another in which he should unite that science with his proper profession of divinity, and accordingly commenced his Demonstration of the Being and Attributes of the Deity,--a performance on which his popular fame now principally rests. When finished he transmitted it, in March 1690, to his friend Dr Tancred Robinson, who disposed of it agreeably to his directions; so that it made its appearance in the following year. One of his reasons for writing this admirable treatise he expresses in the following words:--"By virtue of my function I suspect myself to be obliged to write something in divinity, having written so much on other subjects; for being not permitted to serve the church with my tongue in preaching, I know not but it may be my duty to serve it with my hand by writing; and I have made choice of this subject, as thinking myself best qualified to treat of it. If what I have now written," he continues, "shall find so favourable acceptance as to encourage me to proceed, God granting life and health, the reader may expect more; if otherwise, I must be content to be laid aside as useless, and satisfy myself in having made this experiment."