History of the barometer

The first barometer – a mercurial barometer – was invented in 1643 by Evangelista Torricelli. This Italian physicist was the first to demonstrate the existence of atmospheric pressure. During his experiments, he noticed that the height of the mercury in the tube varied with meteorological changes. His Italian contemporary, the 17^th-century Irish physicist and chemist Robert Boyle, was the first to use the term “barometer”, from the Greek baros : “weight, gravity”.On an 18^th-century barometer like the one shown here, the mechanism developed by Torricelli is located at the back. The atmospheric pressure exerted by the air in the tube on the mercury activates the pin on the dial. The interest in science at the time led craftsmen to combine barometers and thermometers, as is the case here.

History of the thermometer

Traditionally attributed to Galileo, who defined its principle, the invention of the thermometer dates to the mid-17^thcentury. It was at this time that the thermometer was developed to measure temperature by dilating a liquid contained in a glass tube.

Over the course of the 17^th and 18^th centuries, several physicists perfected this instrument, proposing different scales before the adoption of today's scales. In 1654, the Grand Duke of Tuscany, Ferdinand de' Medici, created an alcohol thermometer with 50 graduations. But it wasn't until 1717 that the German Fahrenheit invented the first mercurial thermometer and the scale that bears his name. Then, in 1742, the Swedish Celsius devised a scale ranging from 100°C for freezing water to 0°C for boiling, a gradation that would be reversed after his death. In 1794, the French Convention approved this scale of degrees centigrade, which took several years to become established in France, where it was rivaled by the Réaumur scale presented here. However, the Celsius scale remains the most widely used today.Mercury or alcohol thermometers can be either direct-reading or dial-reading. In the latter case, a mechanism connects a float placed in the column to a pin.

At the end of the 17^th century, thermometers and barometers left the scientists’ laboratories and entered the homes of enlightened people. As part of the encyclopedic collections of the 18^th century, instruments and machines became increasingly appealing, as much for their decoration and the preciosity of their materials, as for the beauty of their form. With science taking a growing place in society, princes or wealthy aristocrats liked to own instruments associating them with the latest discoveries. While the manufacture of barometer and thermometer mechanisms required the very special skills of an optician, that of the object was entrusted to carpenters who created cases for these instruments.

Antonio Carcano said Carcani or Carcany (circa 1755-1820)

A manufacturer of thermometers, barometers and scientific instruments of Italian origin, Antoine Carcano was born around 1755. Initially established at 37, Rue de la Roquette in the Faubourg Saint-Antoine district of Paris, he later moved to 2, Place Dauphine on the Île de la Cité. This last prestigious address testifies to his success, which enabled him to become “constructeur de baromètres et instruments scientifiques pour l'Ecole Royale Militaire” [manufacturer of barometers and scientific instruments for the Ecole Royale Militaire] in 1786. His signature also bears witness to his new social standing. After initially using his surname, Carcano (sometimes Carcani or Carcany), he changed it to “le sieur Carcarno” [the sire Carcano], followed by his address in the Faubourg Saint-Antoine, specifying that he was based ’a coté La fontaine charonne au Ladons Royaux” [next to the Charonne fountain at the Ladons Royaux] where he built this thermometer-barometer. Later, he would further emphasize his professional success by adding that he was a “builder of barometers for the Ecole Royale Militaire” and specified his new location at Place Dauphine.

On October 12^th, 1792, after serving for a month as a citizen soldier and Bastille gendarme in the 48^th Popincourt Battalion, Antoine Carcano sent a letter to the Secretary of the National Convention requesting that “his petition be sent to the Minutes, War and Military Committees, so that he can carry out his experiments ”

Antoine Carcano also enjoyed an international clientele. In 1787, he supplied the English optician Peter Dollond (1731-1821) in London with tubes for his barometers marked “Fecit Carcano”, while on August 30^th, 1813, the Anglo-American physicist Benjamin Thompson, known to posterity as Rumford (after his title of Earl of Rumford), presented a thermometric vase made by Carcano that he used in his research on heat radiation. Seven years later, the American professor William Davis Merry Howard published a description of Carcano's differential thermometer, which he had just received, confirming that the French scientist was able to resume his activity after the French Revolution, and return to his workshop on the Île de la Cité.