Category Archives: Weather

Over the rainbow

Recently, I was lucky enough to visit the mighty Victoria Falls. As I stood at the falls’ edge drenched in spray, I spotted double rainbows formed by sunlight being refracted through the water droplets.

A rainbow, with a fainter secondary companion above, at Victoria Falls. (Alison Boyle)

One of the first people to explain how rainbows form was the Persian mathematician Kamal al-Din al-Farisi, who was born around 1260. Using a glass sphere filled with water to represent a raindrop, he showed that sunlight is bent as it enters the drop, reflects off the back of the drop, and is bent again on its way out. If rays are reflected twice inside the drop, a secondary rainbow is formed with the colours reversed. Here’s a more detailed explanation. Around the same time Theorodic of Freiberg performed a similar experiment. The two were not in contact, but both had been influenced by Ibn al-Haytham‘s Book of Optics. You can find out more about al-Farisi and al-Haytham in the 1001 Inventions exhibition.

Rainbows have fascinated people for centuries, as this illustration from 1535 shows. (Science Museum)

Isaac Newton explained that the rainbow’s colours arise as a result of white light being split into its constituent colours. Many people will have childhood memories of making a Newton colour wheel with a disc of cardboard and a pencil. Here’s a late 19th century version.

A 19th century demonstration apparatus. (Science Museum)

As our understanding of the nature of light has continued to change, so has our understanding of the rainbow. For a detailed account of how people have portrayed rainbows in science and beyond, check out Raymond Lee and Alastair Fraser’s The Rainbow Bridge: Rainbows in Art, Myth and Science.

Capturing clouds in science and art

You might wonder what this watercolour is doing in our Making the Modern World gallery. The chalky cliffs, thatched cottage and country children make a pleasant enough pastoral scene, but what does it have to do with science?

Watercolour by Edward Kennion with cloud study by Luke Howard

Watercolour by landscape artist Edward Kennion, c. 1807, based on a cloud study by Luke Howard (Science Museum / Science & Society)

The clue is in the sky, which represents ‘Cumulus breaking up; cirrus and cirrocumulus above’. These were the new names for the clouds, created by the meteorologist Luke Howard.

Portrait of Luke Howard by John Opie

Luke Howard, by the leading society portrait painter John Opie, c. 1807 (Science Museum / Science & Society)

Howard was a commercial chemist who rose to fame after lecturing “On the Modification of Clouds” in 1802 to the Askesian Society, a scientific club founded by three young London Quakers. He proposed that, rather than being fleeting and innumerable, clouds could be reduced to just three families: cumulus, stratus and cirrus. Combinations were possible and clouds could change from one type to another. Howard was hailed as a genius who had grasped the clouds and brought them within the reach of science.

Cumulus, by Luke Howard

Cumulus in high wind, c. 1803, by Luke Howard. Howard used sketches to illustrate his talk and publications (Science Museum / Science & Society)

Amongst artists his reception was mixed. The German Romantic painter Caspar David Friedrich, for example, worried that ‘to force the free and airy clouds into a rigid order and classification’ would damage their expressive potential and even ‘undermine the whole foundation of landscape painting’.

John Constable disagreed, arguing that ’Painting is a science and should be pursued as an inquiry into the laws of nature. Why, then, may not landscape painting be considered a branch of natural philosophy, of which pictures are but the experiments?’ His cloud experiments have fascinated critics ever since.

British Rail poster, 1990

British Rail poster, 1990. Constable's cloudy landscapes have become emblematic of the British countryside. (Science Museum / Science & Society)

The man with the weather eye

Towards the close of 1837 Patrick Murphy announced that January 20th would be the coldest day of the coming year. The day duly arrived and bitter cold confirmed the prediction. Booksellers were besieged by hordes of people demanding copies of Murphy’s Weather Almanac, which contained predictions for the whole year based on planetary and lunar influences. Murphy made his name as a weather prophet and a small fortune too, but he didn’t escape criticism.     

Caricature of Murphy entitled "The Man with the Weather Eye"

This satirical cartoon references a comic play, in which a learned gentleman mistakes a potato seller named Murphy for the famous meteorologist. The telescope, moon and stars are references to Murphy's astrometeorological theories. (Science Museum / Science & Society)

To some, astrological almanacs simply betrayed the credulity of the British public. However in the 19th century ‘scientific’ and ‘non-scientific’ understandings of weather were not clearly distinguished.  

Take Robert Fitzroy. Better known as the captain of HMS Beagle, the fellow of the Royal Society headed the newly formed Meteorological Department of the Board of Trade (later the Meteorological Office) from 1854. Fitzroy was no astrologist but he did speculate that the moon influenced atmospheric conditions. And many shared his hope that, with sufficient data, predicting the weather might one day become as reliable as predicting the motions of the heavens.   

Fitzroy’s Department had two aims: collecting ‘accurate and digested observations for the future use of men of science’ and, more practically, aiding navigation. Fitzroy supplied instruments and charts to ships’ Captains, who in return sent meteorological data back to London. He also loaned barometers to coastal villages to help fishermen plan their work safely.       

Detail of a Fitzroy storm barometer, c. 1880

Fitzroy storm barometer, c. 1880 (Science Museum / Science & Society)

Using telegraphy, Fitzroy gathered daily reports from a growing network of British and European observers. From 1861 he used this data to produce the first ’forecasts’, which were printed in the newspapers. They were eagerly consumed. However, some members of the scientific establishment worried that they blurred the boundaries between elite and popular forms of knowledge making.   

In 1866, following Fitzroy’s death, an official report found that ”the truth of [Fitzroy's forecasts] is warranted neither by science nor by experience”. Like Murphy’s almanac, they caused the public “to confuse real knowledge with ill founded pretences” and threatened the reputation of “true science”.  Against considerable resistance, the service was cancelled and for a time weather prediction was left to the successors of Patrick Murphy and his fellow weather prophets.

“More Sensitive than the Most Perfect Barometer”

One of the most curious meteorology objects I’ve discovered recently is the weather glass. It was first described in 1558 by the Italian scholar Giambattista della Porta.    

Giambattista della Porta

Giambattista Della Porta (c.1535-1615) surrounded by representations of his many interests, which included natural history, astrology, alchemy, mathematics and natural philosophy (Science Museum Library / Science & Society)

Della Porta’s apparatus was essentially the same as the air thermoscope, which I wrote about a recently. The alternative design shown below was in use from the 1600s. As the air in the vessel expands and contracts water moves up and down the spout, indicating changing atmospheric conditions. 

Weather glass

Weather glass, 1700-1900 (Science Museum / Science & Society)

Before air pressure was understood, the instrument was sometimes called a perpetuum mobile – perpetual motion – because the water level fluctuated with no known cause.

The English physician and mystic Robert Fludd (1574-1637) interpreted the weather glass as a ‘key to two worlds’. For him, it was a microcosmic symbol of the universe and a model for the human body. Others claimed that it could predict the weather days, weeks or even months in advance.  

By the 1660s leading experimental philosophers, who had recently begun to distinguish between temperature and air pressure and to use the thermometer and barometer respectively to measure them, tended to dismiss the weather glass since it responded to both variables.

However, it remained attractive for domestic use due to its simplicity, and portability: one maker claimed in 1917 that his was ‘More Sensitive than the Most Perfect Barometer’. Weather glasses can be bought on ebay and are still popular with amateur weather forecasters today. 

And whilst Fludd’s occult philosophy fell out of favour, some of his ideas persisted. Throughout the 1700s and 1800s many people continued to regard the weather glass and the barometer as reflections of the human body and psyche, since instruments and humans were both influenced by atmospheric conditions. 

Pamphlet by John Patrick, c.1710

Around 1710, John Patrick advertised this barometer/mirror combination, encouraging users to dress for the weather and perhaps reflect on the air's influence on their own health or mood (Science Museum / Science & Society)

150 years of the British Rainfall Organisation

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”. 

George James Symons

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.

Luke Howard's Rain Gauge, 1818

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.  

Kiff mushroom rain gauge exposure meter

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… 

Toad buying an umbrella

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

A lot of hot air?

How did you enjoy the hottest day of the year so far on Sunday? It got me thinking about what else we have in the collection relating to temperature.
For simplicity, I like this modern reconstruction of an apparatus which Philo of Byzantium devised back in 200 – 100 BC to indicate temperature change. A hollow, lead globe is attached to a tube, which is bent over into a container of water. You can probably guess what happens when the globe is warmed…
Reproduction of Philo's thermoscope

Reproduction of Philo's apparatus for indicating temperature change (Science Museum / Science & Society)

Philo explained:  

I assert that when the globe is placed in the sun and becomes warm, some of the air enclosed in the tube will pass out … into the water, setting it in motion and producing air bubbles, one after the other. If the globe be placed in the shade … then the water will rise through the tube and flow into the globe. 

Some seventeen or so centuries later Philo’s idea was revisited, leading to the invention of the air thermoscope. The Italian physician Santorio Santorio was one of several Europeans working on it simultaneously.

Illustration of Santorio's air thermoscope

The two pieces of string tied round this air thermoscope indicate a rise in temperature. From Sanctorii Sanctorii, ... Ars de statica medicina, etc., 1625 (Wellcome Library, London)

Santorio’s instrument is in two parts. The glass bulb and tube are heated to expel some air, and the end of the tube is inverted into the narrow vessel containing water. As the air inside the bulb cools it contracts, drawing liquid up into the tube.  Once it has been set up, the changing water level indicates rising and falling temperature.

Santorio later put a scale on the thermoscope, creating the first air thermometer.  The air thermometer was supplanted by the more familiar liquid-in-glass thermometer from the 1640s. More on that another time. 

Combined thermometer and alcohol barometer, 1719

Combined thermometer and alcohol barometer, 1719 (Science Museum / Science & Society)

Measuring sunshine

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

Sunshine recorder, Campbell type, c. 1880

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

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

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

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)