`When you can measure what you are speaking about and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind."
This was the view expressed towards the end of the 19th century by the Scottish physicist William Thompson, better known by his later title, Lord Kelvin.
Two-hundred-and-fifty years before Kelvin's time, there was no accepted method of assigning a number to temperature in the way we do today, but it was a matter receiving great attention.
Between the years 1641 and 1780, at least 35 different scales of temperature were proposed and came into limited use. Indeed, in those days anyone who constructed a new type of thermometer seemed to throw in a new scale for good measure.
The Fonlex Scale, for example, had a freezing point of -33 degrees and a boiling point of 245; on the Paris Scale the corresponding points were 24.5 and 238, on the Cruquis 106 and 151, and on the Edinburgh Scale, 8 and 47. Two others were constructed in such a way as to give diminishing numbers for increasing temperatures. The Royal Society Scale had a freezing point of 79 and a boiling point of -170 and the De Lisle ranged from 150 down to zero.
By the late 19th century, however, the candidates for universal acceptance had narrowed down to three - Reaumur, Fahrenheit and Celsius - and in the course of the 20th century, Celsius, previously called Centigrade, emerged victorious everywhere except in the United States. But it might well not have been so, because for a time it seemed likely that the scale of temperature proposed by RenZ Antoine Ferchault de Reaumur might be universally adopted. Instead, it is rarely heard of nowadays.
RenZ Reaumur was French, born in 1683 at La Rochelle. He used alcohol as the fluid for his thermometer, and taking the volume of this liquid at the freezing point of water as being 1000 units, he noticed that when it was immersed in boiling water it expanded to a volume corresponding to 1080 units. It seemed sensible to him, therefore, to divide the interval into 80 equal "degrees".
His scale was devised in 1730, 14 years before that of Celsius, and became widely used throughout much of Europe for 150 years. But, ultimately, the decimal simplicity of the scale devised by Celsius resulted in its being adopted as the norm, and the name of RenZ Reaumur faded to oblivion.