TSCHIRNHAUSEN (Ernfroy Walter)

, an ingenious mathematician, lord of Killingswald and of Stolzenberg in Lusatia, where he was born in 1651. After having served as a volunteer in the army of Holland in 1672, he travelled into most parts of Europe, as England, Germany, Italy, France, &c. He went to Paris for the third time in 1682; where he communicated to the Academy of Sciences, the discovery of the curves called, from him, Tschirnhausen's Caustics; and the Academy in consequence elected the inventor one of its foreign members. On returning to Italy, he was desirous of perfecting the science of optics; for which purpose he established two glass-works, from whence resulted many new improvements in dioptrics and physics, particularly the noted burning-glass which he presented to the regent.—It was to him too that Saxony owed its porcelane manufactory.

Content with the enjoyment of literary same, Tschirnausen refused all other honours that were offered him. Learning was his sole delight. He searched out men of talents, and gave them encouragement. He was often at the expence of printing the useful works of other men, for the benefit of the public; and died, beloved and regretted, the 11th of September 1708.

Tschirnausen wrote, De Medicina Mentis & Corporis, printed at Amsterdam in 1687. And the following memoirs were printed in the volumes of the Academy of Sciences.

1. Observations on Burning Glasses of 3 or 4 feet diameter: vol. 1699.

2. Observations on the Glass of a Telescope, convex on both sides, of 32 feet focal distance; 1700.

3. On the Radii of Curvature, with the finding the Tangents, Quadratures, and Rectisications of many curves; 1701.

4. On the Tangents of Mechanical Curves; 1702.

5. On a method of Quadratures; 1702.