ment to the Encyclopædia Britannica. In 1819, on the death of professor Playfair, whose promotion had formerly made room for him in the chair of mathematics, he was elevated to the professorship of natural philosophy, by which his powers were of course brought into a far wider field of display and of usefulness, than they had been for the preceding fourteen years. Among the preliminary treatises of the seventh edition of the Encyclopædia Britannica, which began to be published in 1830, he wrote a "Discourse on the History of Mathematical and Physical Science, during the eighteenth century," which may be described as one of the most agreeable and masterly of all his compositions.
The income enjoyed by Mr Leslie was for many years so much above his necessities, that he was able, by careful management, to realise a fortune not far short of ten thousand pounds. Part of this he expended, in his latter years, upon the purchase and decoration of a mansion called Coates near his native village, where he spent all the intervals allowed by his college duties. Early in the year 1832, at the recommendation of the lord chancellor (Brougham), he was invested with a knighthood of the Guelphic order, at the same time that Messrs Herschel, C. Bell, Ivory, Brewster, South, and Harris Nicolas, received a similar honour. Sir John Leslie was not destined long to enjoy the well-merited honour. In the end of October, while superintending some of the improvements about his much-loved place, he incautiously exposed himself to wet, the consequence of which was a severe cold. Among the various foibles which protruded themselves through the better powers and habitudes of his mind, was a contempt for medicine, and an unwillingness to think that he could be seriously ill. He accordingly neglected his ailment, and was speedily seized with erysipelas in one of his legs; a disorder at that time raging in Scotland with all the symptoms and effects of a malignant epidemic. On Wednesday, October 31st, he again exposed himself in his grounds, and from that day, the malady advanced very rapidly. On the evening of Saturday, November 3d, he breathed his last.
The scientific and personal character of Sir John Leslie has been sketched with so bold and free a pencil by Mr Macrey Napier, his brother in both academic and literary labours, that we make no apology for presenting it to the reader, in lieu of any thing of our own:
"It would be impossible, we think, for any intelligent and well-constituted mind, to review the labours of this distinguished man, without a strong feeling of admiration for his inventive genius and vigorous powers, and of respect for that extensive knowledge which his active curiosity, his various reading, and his happy memory had enabled him to attain. Some few of his contemporaries in the same walks of science, may have excelled him in profundity of understanding, in philosophical caution, and in logical accuracy; but we doubt if any surpassed him, whilst he must be allowed to have surpassed many, in that creative faculty—one of the highest and rarest of nature's gifts—which leads, and is necessary to discovery, though not all-sufficient of itself for the formation of safe conclusions; or in that subtilty and reach of discernment which seizes the finest and least obvious relations among the objects of science—which elicits the hidden secrets of nature, and ministers to new combinations of her powers. There were some flaws, it must be allowed, in the mind of this memorable person. He strangely undervalued some branches of philosophical inquiry of high importance in the circle of human knowledge. His credulity in matters of ordinary life was, to say the least of it, as conspicuous as his tendency to scepticism in science. It has been profoundly remarked by Mr Dugald Stewart, that 'though the mathematician may be prevented, in his own pursuits, from going far astray, by the absurdities to which his errors lead him, he is seldom apt to
