1691 in science

The year 1691 in science and technology involved some significant events.

Biology

 * Italian Jesuit scholar Filippo Bonanni publishes the results of his microscopic observations of invertebrates in Observationes circa Viventia, quae in Rebus non-Viventibus.

Mathematics

 * Gottfried Leibniz discovers the technique of separation of variables for ordinary differential equations.
 * Michel Rolle invents Rolle's theorem.

Medicine

 * Anton Nuck's Adenographia curiosa et uteri foeminei anatome nova is published at Leiden, including a description of the canal of Nuck and a demonstration that the embryo is derived from the ovary and not the sperm.

Technology

 * Edmond Halley devises a diving bell.
 * In music, the "equal temperament scale" used in modern music is developed by organist Andreas Werckmeister.

Births

 * November 18 – Mårten Triewald, Swedish mechanical engineer (died 1747)

Deaths

 * January 17 – Richard Lower, English physician who performed the first direct blood transfusion (born 1631)
 * December 31 – Robert Boyle, Anglo-Irish chemist (born 1627)