Oct. 29, 1675: Leibniz ums It All Up, Seriesly

On October 29, 1675, Gottfried Wilhelm Leibniz made the first use of the long s, ∫, for integral, helping him to discover integral and differential calculus. From the article:

"Oct. 29, 1675: Leibniz ∫ums It All Up, Seriesly

1675: __Gottfried Leibniz writes the integral sign ∫ in an unpublished manuscript, introducing the calculus notation that's still in use today.

Leibniz was a German mathematician and philosopher who readily crossed the lines between academic disciplines. He had a doctorate in law, served as secretary of the Nuremberg alchemical society and fancied himself a poet.

He also conducted diplomatic missions in London and Paris. While visiting those cities, Leibniz acquainted himself with such scientific luminaries as Christiaan Huygens, Robert Boyle, Robert Hook, John Pell and Jacques Ozanam. He showed an unfinished calculating machine to the Royal Society, which elected him a fellow.

Leibniz discussed with his English colleagues his interest in summing series and the geometry of infinitesimals, and he corresponded with them when he was back in France. They apprised him of books in the field and also told him about Isaac Newton's yet-unpublished work on the subject."