Barometer-thermometer of carved and gilt wood

France, Louis XVI period, circa 1770
Carved and gilt wood

This barometer- thermometer presents ‘’ to amortization’’ a vase containing a bouquet of flowers based on scroll decorated with sculpted garland.
In the center a thermometer surrounded by a pearl frame surmounts a tondo shaped barometer also decorated with pearls.
The barometer's circular dial is flanked by sculpted scrolls adorned with flower garlands and rests on an architectural structure.
The lower end consists of a leafy base ending in a seed.

History of the barometer
The first barometer, a mercury barometer was invented in 1643 by Evangelista Torricelli. This italiens physician was the first to demonstrate the existence of atmospheric pressure. During his experiments, he noticed that the height of the mercury in the tube varies with changes in the weather.
On an 18th century barometer, as is the case here, the mechanism according to Torricelli is behind. The principle being that the pressure exerted by the air in the tube (atmospheric pressure) on the mercury makes it possible to actuate the needle of its dial.
The Irish physicist and chemist Robert Boyle was the first to use the term "barometer" from the Greek baros: "weight, gravity".
The interest of the time for science leads artisans to associate, as it is the case here, barometer and thermometer.

History of the thermometer
Traditionally attributed to Galileo, who defined the principle, the invention of the thermometer dates back to the middle of the 17th century. The temperature is measured by the expansion of a liquid contained in a glass tube. Several physicists from the 17th and 18th centuries gradually perfected this instrument and proposed different scales before adopting the current scales. The Grand Duke of Tuscany Ferdinand de Medici created in 1654 an alcohol thermometer with 50 graduations but it was not until 1717 that the German Fahrenheit invented, the first mercury thermometer and the scale that bears his name. Then in 1742 the Swedish Celsius invented a scale ranging from 100 ° for freezing water to 0 ° for its boiling which will be reversed after his death. In 1794, the Convention approved this scale of degrees centigrade which is today the most used.
The mercury or alcohol thermometer can be direct reading or dial. In this case, a mechanism connects a float placed in the column to a needle.

It was at the end of the 17th century that the old thermometer and barometer left the laboratories of scientists to be admitted into the interiors of enlightened people. Indeed, in the 18th century, instruments and machines became more and more appreciated, within the framework of the 18th century encyclopedic collections both for their decoration, the preciousness of their materials but also for the beauty of their form. The sciences taking a growing place in society at that time, princes or wealthy aristocrats were pleased to have instruments associating them with the latest discoveries. If the manufacture of the mechanisms of barometers and thermometers requires the very special skills of an optician, that of the object is entrusted to the carpenters who create cases for these instruments in the image of this barometer-thermometer.

Bibliography
Camille Frémontier-Murphy, « Une collection d’instruments scientifiques au musée du Louvre, », L’Estampille-L’Objet d’Art, n°342, Décembre 1999, p. 40-53