Monge, Gaspard (1746–1818)

French mathematician and chemist, the founder of descriptive geometry. His application of analysis to infinitesimal geometry also paved the way for later developments.

Monge was born in Beaune, Burgundy, and studied at the Collège de la Trinité in Lyon. In 1771 he was drawn into the scientific circle attached to the Academy of Sciences in Paris, and in 1780 he was given official duties as assistant geometer to the Academy. In 1785 he was appointed examiner of naval cadets by the French government. By the time the French Revolution broke out in 1789, Monge was an active supporter of the radicals. He was appointed minister of the navy in 1792, but was forced to resign the following year. As a member of the Committee on Arms 1793–94, he supervised the Paris armaments workshops and helped to develop military balloons. He also served on the commission to standardize weights and measures. He was instrumental in establishing the institution that became the Ecole Polytechnique, was briefly its director, and taught there until 1809.

In 1796, Monge's friendship with Napoleon began. He was sent to the newly conquered Italy as a member of various commissions. In 1798 he assisted in the preparation for the Egyptian campaign; he then accompanied Napoleon and was appointed president of the Institut d'Egypte established in Cairo. Monge also went with Napoleon on expeditions to the Suez region and Syria in 1799. Subsequently Napoleon appointed him a senator. When Napoleon was overthrown in 1815, Monge was discredited.

Independently of French chemist Antoine Lavoisier, Monge synthesized water in 1783, but he also worked with Lavoisier in 1785 on the synthesis and analysis of water. Monge quickly embraced Lavoisier's new chemistry and played an energetic part in getting it accepted.

Monge asserted the autonomy of analytical geometry as a separate branch of mathematics. In particular, he devoted himself to the families of surfaces as defined by their mode of generation, and the properties of surfaces and space curves. He also established the distinction between ruled surfaces and developable surfaces.

In a paper on infinitesimal geometry in 1776 Monge introduced lines of curvature and the congruences of straight lines. His main work is Géométrie Descriptive/Descriptive Geometry (1799).