Transcribed by PA Brewery Historian Rich Wagner 08-14-2025
The Western Brewer May 1915
A Brief History of the Thermometer
…Many people are credited with the invention of the thermometer, Drebble, a Hollander, being referred to more than any other; but to Galilleo Galilei the laurels should probably be handed. According to history, it seems that about 1592 he invented at Padua an instrument described as “a glass containing air and water, to indicate changes and differences in temperature.”
With the idea started, the Grand Duke of Tuscany investigated this invention and improved it more or less between 1630 and 1640. The original thermometer consisted of a glass tube about 16” long with a hollow ball, or bulb, at the end The whole was heated until the air inside became rarefied, when the open end was placed in water, the tube being kept upright. As the air in the tube cooled or contracted, the fluid (water was originally used) rose to a certain point and any subsequent changes caused the level of the fluid to be either elevated or depressed.
This was used by Sanctorius as a “heat measure,” or fever thermometer. It is on record that he had his patients hold the top of the thermometer so the level of the fluid would be arrested at a point equal to the temperature of the person holding it. A point was undoubtedly determined by a normal, healthy person beforehand, and it is reasonable to assume that Sanctorius drew his deductions by noting the distance above or below this “normally healthy” person.
Before ten years had passed the Grand Duke of Tuscany had carried out his idea of first partly filling the tube with alcohol and closing the open end, thus sealing it and excluding the air. Realizing that the level of the liquids in these various instruments meant nothing, pupils of Galileo sought to make a scale of temperature and melted onto the tube of their thermometers small glass balls about the size of a pin’s head, the zero of the scale being the point to which the liquid fell in a freezing mixture of salt and water.
At the time the bright minds of Europe decided that the freezing point of liquids varied to such an extent that it could not be used as a test point, and suggested taking the temperature in a cave cut straight into the bottom of a cliff fronting the sea to the depth of 130 feet, with 80 feet of earth about it.
About 1662, Hooke, placing his instrument in freezing distilled water, marked “zero” at the top of the column of spirit after immersion of the bulb. Soon after this he suggested that the second point should be the boiling point of water, but this was not adopted at the time. Delance suggested that the freezing point of water should be marked “cold” (-10°) the melting point of butter “hot” (+10°) and the space midway between “temperate” (0°), with ten divisions between each.
In 1714 Fahrenheit arranged a scale for thermometers that showed the freezing of water at 32° and the boiling point of water at 212°. Many suggestions have been made as to why h graduated the freezing and boiling of water into 180 divisions, one being that as he was an astronomical instrument maker and as his machines divide to full circles (360 divisions), he used a half circle for his scale. Seventeen years later Réaumur, a French physicist, brought out a scale on which the freezing point of water appeared as 0°, the distance between this and the boiling point of water being divided into eighty equal parts. Anders Celsius, professor of astronomy at the University of Upsala, proposed a scale in 1742 and called the freezing point of water 100° and the boiling point of water 0°.
These points were afterward reversed by Christin of Lyons (France) in 1843, and the result is the well known Centigrade scale. Athanasius Kircher was the first to use quicksilver in thermometers. Quicksilver and alcohol have been accepted by the scientific world as convenient and accurate means to indicate the temperature of anything which the tube containing them may come in contact.
For high temperatures quicksilver is used, as it freezes at about -38°F (-39°C) and boils at 662°F (+357 C). As the freezing point of mercury is fairly high, alcohol thermometers are invariable used in very cold climates. This liquid freezes at -203°F (-130.5°C) and boils at 173.5°F (+78.5°C).
From the foregoing it will be seen that quicksilver is unsuitable for any very low temperature and alcohol is unsuitable for any very high temperature…