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By Victoria Carroll on

Coming Out Of The Cold

It looks like spring is finally here.   

Daffodils (Anvica)
Daffodils (Anvica)

 About time too, after the coldest UK winter for over 30 years.  The figures are in, and this year the mean temperature for 1 December – 24 February was just 1.51 °C, compared to a long-term average of 3.7 °C.

But if you think that’s bad, cast your mind back to The Big Freeze of 1962/63, when parts of Wales and the South West were buried under snowdrifts six metres high, the Thames froze, and over 400 Football League and Cup games had to be cancelled. 

Ice under Windsor Bridge, January 1963 (Image:

That year the UK’s mean winter temperature was a bone-chilling -o.18 °C, making it the coldest since 1740.     

Coincidentally, it was around 1740 that the Swedish natural philosopher Anders Celsius began conducting experiments aimed at devising a scientific, international temperature scale.   

Portrait of Anders Celsius, c. 1730s
Anders Celsius, c. 1730s (Science Museum / Science & Society)

At the start of the 1700s, temperature was measured in inches of mercury or alcohol, up and down from arbitrary zero points. In 1724 the German natural philosopher Daniel Fahrenheit proposed a scale based on three points, which set the melting point of water at 32 degrees. A number of  rival scales also came into use. 

Photograph of alcohol thermometer by Casartel, Amsterdam, 1720-50
This alcohol thermometer was marked with Florentine and Fahrenheit scales c. 1720-1750 (Science Museum / Science & Society)

Celsius recognised that a common, international temperature scale would be useful for scientific purposes. He first conducted experiments to confirm how the freezing and boiling points of water varied with latitude and altitude. He then selected these as his fixed reference points and placed 100 gradations between them. A little known fact: in 1742 Celsius originally defined zero degrees on his Centigrade scale as the boiling point of water and 100 degrees as freezing point. The scale was reversed a few years later – but if it hadn’t been then we would have recorded this winter’s average temperature as 98.49 °C. 

Photograph of a French thermometer with the centigrade scale by Pierre Casati, c. 1790
An inscription on this mercury thermometer, c. 1790, notes that the original scale has been reversed to place freezing point at zero degrees (Science Museum / Science & Society)

One comment on “Coming Out Of The Cold

  1. In 1743, the Lyonnais physicist Jean-Pierre Christin, permanent secretary of Societé Royale de Lyon, who had worked independently of Celsius, developed a scale where zero represented the freezing point of water and 100 represented the boiling point of water. On 19 May 1743 he published the design of a mercury thermometer, the “Thermometer of Lyon”, built by the craftsman Pierre Casati, that used this scale (last image).

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