The invention of a barometer everywhere attribute Evanguelisto Torricelli in 1643. However historical documents say that the first water barometer was constructed unconsciously by the Italian mathematician and the astronomer Gasparo Bertie between 1640 and 1643.
Gasparo Bertie's experiment
Gasparo Bertie (about 1600 — 1643) was born, most likely, in Mantua. He carried out a big part of the life in Rome. Famous he was made by an experiment during which it, that without knowing, constructed the first working barometer. It has also works in the field of mathematics and physics.
In 1630 Giovanny Baptiste Baliani sent a letter to Galileo Galilei in whom said that his pump of siphon type cannot lift water one height bigger than 10 meters (34 feet). In the answer Galilei assumed that water is lifted by a vacuum, and force of a vacuum cannot hold more water as a rope cannot sustain too big weight. On the representations dominating then, the vacuum could not exist.
Soon Galilei's ideas reached Rome. Gasparo Bertie and Raphael Madzhotti developed an experiment to check existence of a vacuum. Bertie constructed a 11-meter pipe, filled it with water and sealed on both sides. Then one end was shipped in the container with water and opened it. A part of water followed, but about ten meters of a pipe remained filled, as well as predicted Baliani. The space over water had to look for explanations. Explanations within the dominating theory rejecting a vacuum was whole two. It agrees to the first, water gives rise "spirits". "Spirits" fill space and force out water. It agrees to the second, more widespread argument offered by Descartes, the space over water fills air. Air - so thin substance that can get through a time in a pipe and force out water.
Evanguelisto Torricelli's explanation
Evanguelisto Torricelli, the pupil and Galilei's friend, dared to look at a problem from a different angle. He assumed that air has weight, and the weight of air holds water in a pipe at the level of about ten meters. Before considered that air is weightless and its thickness does not put any pressure. Even Galilei perceived this statement as the infallible truth. If the assumption of the weight of air is right, liquid heavier than water has to fall in a pipe below, than water. Torricelli shared such forecast with the close friend Vincenzo Viviani and suggested to use mercury as a barometer. At the beginning of 1644 Viviani made an experiment in which he showed, the mercury weighing in fourteen times more waters fell in a tube to a mark fourteen times smaller than to what water fell. It would seem, Torricelli's ideas were confirmed. However philosophers of old school claimed, mercury, as well as waters, makes "spirits". And "spirits" of mercury are stronger than "spirits" of water therefore mercury falls below water. The end to a dispute was put by Blaise Pascal and his pupils Pierre of Petya and Florin Perye. The last took measurements of a column of mercury in mountains and at their bottom. Results were various that confirmed supporters of the idea of atmospheric pressure. Torricelli is traditionally considered the inventor of a barometer because he the first suggested to use it as the device for measurement, but not for "production of a vacuum".