On Saturday I went to a conference commemorating the 150th anniversary of the foundation of the British Rainfall Organisation (BRO), organised by the history group of the Royal Meteorological Society. Here’s what I discovered…

The British Rainfall Organisation demonstrates the importance of networks in meteorology. It was founded in 1860 by George James Symons to coordinate rainfall observations by volunteers “of both sexes, all ages, and all classes”. 

Symons was known as kind man, who was supportive of his volunteers and had a twinkle in his eye (Science Museum / Science & Society)

Every morning at 9am hundreds of observers across the country (by 1900 there were 3,408 stations in Symons’s network) scurried into their back garden to inspect their rain gauges. They sent their results back to Symons, who analysed them and published them in British Rainfall magazine. In 1919 the BRO was taken over by the Met Office (who now make some of their rainfall data available online). However, ‘amateur’ observers still make important contributions to meteorology today, and I met some of them at the conference.

This particular rain guage, made in 1818, belonged to the famous meteorologist Luke Howard (Science Museum / Science & Society)

Site inspections and other quality control measures are an important aspect of managing any observation network. During a talk about the present-day rainfall network, I found out what this shiny instrument in our collection is for.  

A common issue with rain gauges is how exposed they are to wind, with very sheltered and very open sites both leading to inaccuracies. During a site inspection, this instrument is placed on top of the gauge and the domed surface reflects all the nearby obstacles – fences, hedges, buildings, etc. The scale allows exposure to be measured.

Clever. But everyone knows what the most useful, mushroom-like, rain-related instrument really is… 

This print, produced around 1845, satirised the fashion for umbrellas (Science Museum / Science and Society)

The recent sunny spells have got me thinking about some of my favourite objects in the meteorology collection – sunshine recorders.

Campbell sunshine recorder c. 1880 (Science Museum / Science and Society)

John Francis Campbell (1821-1885), of the Hebridean island of Islay, designed the apparatus pictured above. You may be able to figure out how it works just from looking at it…

The idea is that the glass ball acts as a lens, focusing the sun’s rays onto an area within the wooden cup and scorching it. As the sun travels from east to west across the sky it burns an arc shape into the wooden bowl, indicating the duration and approximate intensity of sunshine for the day. A single wooden bowl can be used for six months, since every day the sun is slightly higher (leading up to mid summer) or lower (leading up to mid winter) in the sky, so it leaves a separate trace. Simple – but effective.

Campbell’s design was refined by the Cambridge Professor George Gabriel Stokes. Stokes devised a stand, into which special cards are inserted every day to serve as the recording part of the apparatus. This gives more accuracy than the simple wooden bowl.

Campbell-Stokes sunshine recorder, 1899 (Science Museum / Science & Society)

The Met Office still use Campbell-Stokes sunshine recorders today to measure hours of sunshine, although these are gradually being replaced by electronic instruments.

Anyway, enough talk of measuring sunshine. Time to sit back and enjoy it!

Woman in a deckchair, c. 1935 (© NMeM / Kodak Collection / Science & Society)

It looks like spring is finally here.   

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: TheRoyalWindsorWebsite.com)

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.   

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. 

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. 

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)