Mercurial advances

 IN IRELAND it took us nearly three hundred years to go from a German system to a Swedish one, and many are still not converted. Temperature scales, that is, namely Fahrenheit and Celsius.

Some people, indeed, are ‘bilingual’, preferring the excitement of the Celsius scale in winter – ‘the mercury has plunged below zero’ – to the extravagance of Fahrenheit in the summer: ‘temperatures will be in the high seventies’.

Daniel Fahrenheit, from Danzig, came up with the idea of calling 32 degrees the freezing point of water. This was computed on the basis of zero degrees being the freezing point of salt water, 32 degrees being the freezing point of pure water, and 212 being the boiling point of water.

But in 1742, Swedish astronomer Anders Celsius published a paper pointing out that if the freezing point of water was pegged at 100 degrees and the boiling point at zero degrees, then this Centigrade scale could be divided into a hundred – a much easier calibration to work with than Fahrenheit.

The temperature gauge was then tampered with by another Swede.

Whether Carolus Linnaeus was the first person to have formulated the First Law of Laboratory Work (“hot glass looks exactly the same as cold glass”) we can’t be sure. However, after the death of Celsius, Linnaeus reversed the scale so that zero became the freezing point and 100 degrees the boiling point.

Linnaeus, known as the Father of Taxonomy, was the Swedish botanist responsible for the basis of the Latinised nomenclature system for all living things, which gives us the like Trogladytes trogladytes for the wren, Garulus glandarius hibernicus for the Irish jay, Ursus arctos horribilis for the grizzly bear and so on throughout the animal and plant kingdoms.

Amazingly enough Linnaeus boarded with Celsius in Uppsala for a time.

One can only imagine the conversation of an evening between these two scientific over-achievers. Picture, if you will, Carolus leaning against the kitchen table, idly chewing on some gum, or Gummi masticulorum, as he doubtless called it. Fish fingers may have featured on the day’s menu: “I say Anders, do you fancy some Pisces digitalis for your dinner?” “Well, certainly, Carolus, but only if we cook it at a temperature of 60 degrees Me.”

Celsius was finally honoured with the calibration in 1948 by international agreement, although giving the temperature in 'degrees centigrade' was commonplace for many years after.

In scientific circles — and across a range of endeavours which require ultra accurate readings (engineering, food production, medicine, scientific research) temperatures are now given on the Kelvin scale, named after Belfast-born William Thompson, Lord Kelvin. This uses the fixed value of the triple point of water, which is the unique temperature at which the three phases of water (solid, liquid and vapour) co-exist in equilibrium. Defined to be 273.16K exactly, the standard unit, the Kelvin, is thus extrapolated.

The degree Celsius has the same size as the Kelvin, but is offset from the Kelvin scale by 273.15 K to make it conveniently similar to the historical unit, the degree Centigrade. Linnaeus would have been pleased.

Another refinement added in the 20th century to weather charts attempted to objectively work out how cold it actually feels. The wind chill factor measures how wind causes temperatures to seem much parkier than they really are. But scientists have long argued that this system is misleading, and a Thermal Comfort Index was devised to more scientifically convey how cold it is.

During Franco’s rule in Spain, the dictator came up with the ruse of boosting public thermometers a degree or three to encourage visitors when the Spanish tourist trade was only a fledgling industry. It’s a tactic, one suspects, unlikely to work in Ireland. No amount of tinkering with the temperature gauge could persuade you it’s anything other than a raw old day the majority of the time.