In considering Ray's work on geology it has been necessary to give an account of the Discourses; for, as we have seen, these are his fullest treatment of the subject and the only contribution that has received any attention from later writers. But in fact the Discourses both in their intention and in their gradual enlargement follow closely the book which he published in the previous year, 1691.

The Wisdom of God manifested in the Works of the Creation is certainly his most popular and influential achievement. Published as a slim octavo volume of 249 pages, in a first edition of 500 copies, it was reprinted in a second edition of 382 pages in 1692, in a third of 414 pages in 1701 and in a fourth of 464 pages in 1704. It was reissued many times during the next century; it formed the basis of Derham's Boyle Lectures in 1711–12; it supplied the background for the thought of Gilbert White and indeed for the naturalists of three generations; it was imitated, and extensively plagiarised, by Paley in his famous Natural Theology; and more than any other single book it initiated the true adventure of modern science, and is the ancestor of the Origin of Species or of L'Évolution Créatrice.

If botany was the field of Ray's greatest and lifelong interest, it is by no means his only or even perhaps his chief claim to the gratitude of posterity. In it, as we have seen, he accomplished work which would of itself make a fine record: to it, as he constantly claims, he returned from other excursions as to his proper task. But the astonishing feature of his career is not his mastery of a single subject, but the range of his knowledge and the value of his parerga. In these days of specialisation it is difficult to believe that a man could make himself expert in the whole of zoology literally as a sideshow and in the intervals of his main study; and Ray himself never claimed to have done so. But the fact remains that after Willughby's death he set himself to produce books on birds, fishes, mammals and reptiles, and insects; and that these books, even more than his botanical writings, laid the foundation for serious scientific progress in each subject.

It has been customary to regard this aspect of his work as little more than the editing of his friend's material and to give Willughby the credit for the result.

The Historia Plantarum, for all its massive learning, did not achieve the success that it deserved. Ray himself, writing in 1689 to Lhwyd, said ‘as for cuts for my History of Plants there are none to be expected; the book sells not so well as to encourage the undertakers to be at any further charge about it. The times indeed of late have not been very propitious to the booksellers’ trade'; and Sir James Smith, writing more than a century later, declared that though ‘so ample a transcript of the practical knowledge of such a botanist cannot but be a treasure, yet it is now much neglected, few persons being learned enough to use it with facility for want of figures and a popular nomenclature’. It was in fact handicapped, as Ray had foreseen, by the lack of plates; and its bulk made it necessarily a book for the few. It is a monument to its author's greatness, and prepared the way for Linnaeus. But it could hardly do more.

For indeed it was singularly unfortunate in the time of its appearance. Ray lived and worked unmoved by the upheavals of the period: but the men to whom such a book could appeal belonged to the great world; and in Britain that world was in confusion.

Before the Cambridgeshire Catalogue was out of the press Ray had formed plans for further work. The earliest of his letters to Willughby, dated from Trinity College on 25 February 1659, accompanies a gift of the newly published work and continues with proposals:

Ray's work on the British Flora was only one comparatively small part of the output of the years after the publication of the Historia Plantarum. Busy as his life had been, no period of it was so productive as the years between 1688 and 1698; and hardly any writers can ever have produced so many and such varied books in a single decade.

Most of these publications deal with subjects other than botany. For as soon as his magnum opus was finished, he took up the task which Willughby had suggested and Robinson in his letter of 18 April 1684 had revived. The volumes in which he surveyed the Mammals, Reptiles, Birds and Fishes—those hand-books which he regarded as journeyman's work but which actually laid the foundations of zoological study—were finished in 1692 and 1694. They will be discussed in detail later. Here we need only remark that though the second of them, the Synopsis Avium et Piscium, was little more than a condensation of his two larger volumes, the first broke fresh ground and involved not only researches for which he had had little previous training, but the handling of general problems in biology and taxonomy in which he made new and very important contributions to learning.