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 something superhuman!’ The justification of this eulogy rests on what he did during the first thirty years of his life. Apart from more juvenile work, he contributed when scarcely nineteen years old to the ‘Prolegomena’ of the fifth edition of Helvicus's ‘Theatrum Historicum,’ published in 1651, a treatise on the Julian era, which is still useful. When twenty-one years old he had made elaborate drawings to illustrate Dr. Thomas Willis's work on the ‘Anatomy of the Brain’ (ib. p. 227). He was some years afterwards specially requested by Charles II to prepare some drawings of insects microscopically enlarged. This talent of fine and accurate drawing must have been of great use to him in the profession which he subsequently adopted, and indeed may have had much to do with his choosing it. With reference to his skill in this and in experimental manipulation, Hooke writes of Wren in the preface to his ‘Micrographia:’ ‘I must affirm that since the time of Archimedes there scarce ever met in one man in so great a perfection such a mechanical hand and so philosophic a mind.’ Probably about the same period he invented the planting instrument, which, ‘being drawn by a horse over land ploughed and harrowed, shall plant corn equally and without waste, and a method of making fresh water at sea’ (ib. pp. 183 n. and 198), and produced his clearly explained and illustrated scheme for the graphical construction of solar and lunar eclipses and occultation of stars, which was afterwards published in 1681 in Sir Jonas Moore's ‘System of Mathematics,’ p. 533. About 1656 he solved a problem proposed by Pascal to the geometers of England, and retorted by sending a challenge to the French savants—one which had originally been issued by Kepler, and which Wren had himself solved. This challenge was not answered.

Four tracts on the cycloid by Wren were published by John Wallis (1616–1703) [q. v.] in 1658 among his ‘Mathematical Works’ (see i. 533), which Wren had communicated to him; one of these was Kepler's problem, which Wren had solved by means of a cycloid. These tracts on the cycloid show Wren's powerful handling of the old geometry. Demonstrations of this curve are given which are now considered to be proper subjects for the differential calculus; but Wren's solutions preceded by many years the publication of Newton's fluxions or the equivalent method of Leibnitz. It is much to be wished that more records had been preserved of Wren's geometrical demonstrations. The few that do exist quite justify Newton's high opinion (quoted below) of Wren as a geometrician. Hooke in his ‘Cometa’ preserves a beautiful geometrical method of Wren for one of the steps in the graphical determination of a comet's path (see the diagram and text,, App. p. 60).

Wren seems to have taken very little pains to secure for himself the merit of his various inventions, and it was generally believed that Henry Oldenburg [q. v.], the secretary to the Royal Society, was in the habit of communicating Wren's inventions to his friends in Germany, who passed them off for their own. It is through Flamsteed that we are enabled to give Wren the credit of his method of graphical construction of solar eclipses, and it is through Hooke that we learn of his geometry respecting the comet's path (, Posthumous Works, p. 104).

While Wren was still at Oxford, he initiated some experiments (see, Works, i. 41; , Lives, p. 97) on the subject of the variations of the barometer, to test the opinion of Descartes that they were caused by the action of the moon. Observations for the same purpose had taken place near Clermont in France, at the instance of Pascal, about ten years earlier; but the practical use of the instrument as connected with the weather is attributed to Wren, and was so recorded at a meeting of the Royal Society in February 1679 (see also Derham's account of Hooke's experiments published in 1726). About the same date he made experiments which led him to the invention of a method for the transfusion of blood from one animal to another. This appears from a letter of Boyle, dated 1665, in which he speaks of the experiments ‘started by Wren at Oxford about six years agone, long before others, as we know, thought of such a thing.’ At the time very great results were expected from this invention; nor is it now entirely obsolete. Anatomical and medical subjects seem to have always engaged much of Wren's attention. To this he may have been led by sympathy with his sister Mrs. Holder's pursuits, who was very skilful, and is even said to have cured Charles II of a hurt in his hand (, p. 224), and to his own experience as demonstrating assistant to Dr. Scarburgh. Again, his cousin, Thomas Wren, a son of Bishop Matthew Wren, was in his earlier years a practising physician. We also read of Wren himself being busied with an invention for purifying and fumigating sick rooms (Parentalia, p. 213). Twelve pages of the ‘Parentalia’ (pp. 227–39) are devoted to Wren's anatomical and medical pursuits. A study which greatly occupied Wren's thoughts from his college days even