In 1695 David Gregory married Elizabeth, a daughter of Mr Oliphant of Langton. His marriage is commemorated in a Latin ode written by his friend Anthony Alsop, a student of Christ Church, and published in his works.
Shortly after his marriage he brought out his great book, Catoptricae et Dioptricae Sphericae Elementa, which turns out for the comfort of the ignorant to be a great work on looking-glasses and lenses.
The book came as a revelation to many men in that day, for in it Gregory tried to simplify his subject, and to make it clear to the many instead of to the few. He was rewarded with praise, and his book was promised immortality. How changed are things in the present day, when to none of our writers will criticism promise celebrity exceeding at the outside two generations. Keill blossomed out into poetry: ‘It will last as long as the sun and moon endure,’ and it is just possible that it may—in the Bodleian Library!—only that was not what Keill meant.[[2]]
[2]. John Keill, 1671–1721, was born in Edinburgh. Was Professor of Astronomy at Oxford and an active member of the Royal Society. He died of a ‘violent fever’ at Oxford on Thursday, August 31st 1721, a few days after entertaining ‘the Vice Chancellor and other academic dignitaries at his house in Holywell Street with wine and punch.’ He is buried in St Mary’s Church.
Comparatively unnoticed at the time was a suggestion made in this book about mirrors and lenses with regard to following Nature in the construction of a telescope. It was almost certainly Pitcairne who had explained to Gregory the strange mechanism of the human eye, and how in Nature objects before they fall on the retina pass through both the vitreous humour and the crystalline lens. Gregory pointed out that Nature does nothing in vain, and suggested that, in imitation of Nature, the object glasses of telescopes might be composed of media of different density, and that an instrument made on this principle would probably produce much clearer vision than any then in use. After Dollond had brought out his beautiful achromatic glasses the meaning of Gregory’s suggestion became clear, but it is a curious fact that neither James Gregorie, who invented the reflecting telescope, nor David Gregory, who suggested the achromatic telescope, should ever have seen the practical result of their imaginations.
Life in Oxford for Gregory turned out, as is often the case, to be rather different from his anticipations. He had looked forward to years of studious peace; but the reality, while it answered his expectation in giving him much time for study, had surrounded him with men prepared to be unfriendly towards him. ‘The Scotchman’ received much contumely in Oxford, possibly more than would otherwise have been the case, because he was so well known to the outside world. Some of Hearne’s Collections have the full flavour of the sort of annoyance to which he must have been subjected, an annoyance none the less irritating to Gregory because the facts so generally disagreed with the views expressed about him. Compare the two following passages, which are evidently meant to describe the same circumstance.
‘In 1702, David Gregory produced at Oxford his most important treatise, Astronomiae Physicae et Geometricae Elementa. In this were included several propositions communicated by Newton, being results which their author had not obtained at the time of the publication of the first edition of the Principia, but was anxious to bring before the public at once without waiting for the second edition of his own work.’ * * *
‘It may here likewise be observed that men well skilled in Mathematics scruple not to say that David Gregory has stole most of his astronomy from Isaac Newton, whom he has mentioned with some little acknowledgment but not so often as he should have done, which, as ‘tis said, has put Sir Isaac on a new edition of his Principia.’
How different these two stories are it is easy to see, and although Sir Isaac never expressed the sentiments assigned to him by Hearne, nor, it is likely enough, would Gregory ever have this charge made directly to him, yet it is impossible but that the Savilian professor occasionally felt the sting of such mischief-making.
Gregory’s great ally was Dr Charlett, the Master of University College, but besides him, he numbered amongst his friends, Halley, who obtained the Savilian Chair of Geometry, Dr Hudson, Dr Smalridge, Dr Wallis and Dr Aldrich, between each of whom and Gregory, Hearne seemed determined to make bad feeling. As was quite natural, these men, working along the same lines, had often to use each other’s materials, but Hearne always represented Gregory as pirating the results of their labour without acknowledgment. The statement of his indebtedness, only given once, was petulantly regarded as insufficient, and even inverted commas did not mollify his wrath. In fact, Gregory committed the only sin which Dickens says is unpardonable—he was successful—and the commoner men in Oxford, who could not regard anything Scottish without disapprobation, would not forgive him. When Hearne took exception to ‘the Scotchman’s Greek’ he was on safe ground and no one regretted this more than did Professor Gregory himself, who was held up for ridicule by Hearne because ‘men took him for an oracle.’ When he commenced the publication of his edition of the ancient mathematicians, he arranged with Dr Hudson that, while he himself would be responsible for the mathematics, Hudson should see to the correctness of the Greek. In this series too, Gregory and Halley undertook an edition of the Conics of Apollonius, but it was not completed till after Gregory’s death.