Italian physicist and mathematician Evangelista Torricelli
has the credit of his inventing of the mercury barometer around 1644. A barometer
is a scientific instrument used to measure atmospheric pressure. After the invention of mercury barometer, aneroid barometer
was invented in 1843 by French scientist Lucien Vidie.
Born on October 15, 1608 in Faenza, Italy in a poor family, his father Gaspare Torricelli was a textile worker. He was educated with the help and care of his uncle, a Camaldolese monk because his father sent him to his uncle due to insufficient resources they had to provide an education for him.
Mr. Torricelli became the first scientist to create a sustained vacuum and to discover the principle of a barometer. It was Galileo that suggested Evangelista Torricelli use mercury in his vacuum experiments. Torricelli also discovered Torricelli's Law which states that the rate of change of volume of fluid in a draining tank is proportional to the square root of the depth of fluid in the tank. (Definition taken from gershwin.ens.fr)
He also designed and built a number of telescopes and simple microscopes. He died on October 25, 1647 due to contracted typhoid fever.