Besides the previously mentioned works, Playfair was a frequent contributor to the 'Edinburgh Review,' and also wrote the articles 'Æpinus' and 'Physical Astronomy,' in the 'Encyclopædia Britannica.' Francis Jeffrey, of whose elaborate and elegant memoir the above is but a brief summary, speaks of Playfair as being "one of the most learned mathematicians of the age, and among the first, if not the very first, who introduced the beautiful discoveries of the later Continental geometers to the knowledge of his countrymen, and gave their just value and true place in the scheme of European knowledge, to those important improvements by which the whole aspect of abstract science has been renovated since the days of our illustrious Newton;" also, "as possessing in the highest degree all the characteristics both of a fine and powerful understanding, at once penetrating and vigilant, but more distinguished perhaps for the caution and sureness of its march than for the brilliancy or rapidity of its movements; and guided and adorned through all its progress by the most genuine enthusiasm for all that is grand, and the justest taste for all that is beautiful."--_Memoir of John Playfair, by Lord Jeffrey._--_Encyclopædia Britannica._ JOHN RENNIE, F.R.S., L. and E., &c. Born June 7, 1761. Died October 4, 1821. John Rennie was born at Phantassie, in the parish of Prestonkirk, in the county of East Lothian. His father was a highly respectable farmer, who died in 1766, leaving a widow and nine children, of whom John was the youngest. He acquired the first rudiments of his education at the village school, which was situated on the opposite side of a brook. To cross this at certain seasons of the year it was necessary to make use of a boat, which was kept at the workshop of Andrew Meikle, an ingenious mechanic well known in Scotland as the inventor of the threshing machine. Young Rennie, having thus frequent occasion to pass through Meikle's workshop, became deeply interested in the various mechanical operations that were in progress, and a great part of his leisure and holiday time was spent therein. During the evening he employed himself in imitating the machines which had particularly attracted his attention, and when only ten years old succeeded in constructing a model of a steam-engine, a windmill, and a pile-driving machine. At twelve years of age he left the Preston school and entered the service of Mr. Meikle for a space of two years, at the end of which time, finding that a constant application to manual labour retarded the progress of his intellectual faculties, he determined to place himself under the tuition of Mr. Gibson, an eminent mathematical master at Dunbar. Here Young Rennie attained such proficiency in his studies, that when, two or three years afterwards, Mr. Gibson was appointed master to the public academy at Perth, he was able to undertake the temporary management of the Dunbar school. While at this school he