in all cases without fee, he was of great use in the district where he lived. It
was this circumstance alone that prevented the reverend members of the pres-
bytery from calling him to account for his superior intelligence. His son
David, the subject of this sketch, studied for a considerable time at Aberdeen,
but completed his education at Edinburgh. In 1684, when he was only twenty-
three years of age, he made his first appearance as an author, in a Latin work
concerning the dimensions of figures, printed in Edinburgh, and entitled, "Exercitutiones Geometricas." The same year in which this work was published, he was called to the mathematical chair in Edinburgh college, which he held with the
greatest honour for seven years. Here he delivered some lectures on optics, which formed the substance of a work on that science, of acknowledged excellence. Here also Gregory had first been convinced of the infinite superiority of Newton's philosophy, and w r as the first who dared openly to teach the doctrines of the Principia, in a public seminary. This circumstance will ever attach honour to the name of Gregory; for let it be remembered, that in those days this was a
daring innovation ; and Cambridge university, in Avhich Newton had been educated, was the very last in the kingdom to admit the truth of what is now regarded by all as the true system of the world. Whiston, in his Memoirs of his
Own Time, bewails this in "the very anguish of his heart," calling those at Oxford and Cambridge poor wretches, when compared with those at the Scottish universities. In the year 1691 Gregory went to London, as there had been circulated a report that Dr Edmond Bernard, Savilian professor at Oxford, was about to resign, which formed a very desirable opening for the young mathematician. On his arrival in Londoa he was kindly received by Newton, who had formed a very high opinion of him, as we learn from a letter written by Sir Isaac to Mr Flamstead, the astronomer royal. Newton had intended to make Flamstead a visit at Greenwich observatory, with a view to introduce Gregory, but was prevented by indisposition, and sent a letter with Gregory by way of introduction. " The bearer hereof is Mr Gregory, mathematical professor
at Edinburgh college, Scotland. I intended to have given you a visit along with him, but cannot; you will find him a very ingenious person, a good mathematician, worthy of your acquaintance." Gregory could not fail to be highly gratified by
the friendship of two of the greatest men of the age, and most particularly eminent in that department of science, which he cultivated with so much zeal and success. Such a mind as Newton's w r as not likely to form an opinion of any individual, on a vague conjecture of their ability, and the opinion once established would not be liable to change; accordingly we find that his attachment to the interests of the young mathematician, were only terminated by death. In a letter addressed a considerable time afterwards to the same amiable individual, he writes thus, "But I had rather have them (talking of Flamstead's observations upon Saturn, for five years, which Newton wished from him) for the next twelve or fifteen years if you and I live not long enough, Mr Gregory and Mr Halley are young men."
Gregory's visit to London was important to his future fame as a mathematician. He was elected a fellow of the Royal Society, and afterwards contributed many valuable papers to their transactions. At the head of these must be mentioned that which he delivered on his first introduction to their meetings, a solution of the famous Florentine problem, which had been sent as a challenge to the British mathematicians. Gregory's solution, which is extremely beautiful, will be found in the number of the Philosophical Transactions for January, 1694. On the 8th of February, 1692, David Gregory was made master of arts, of Baliol college, Oxford; and on the eighteenth of the same month he received the degree of doctor of physic. At this time he stood candidate with Dr Halley for the
