• Prof Roger Wotton

A bird in the air pump

Updated: 5 days ago

Prof Roger Wotton

Emeritus Professor of Biology


Joseph Wright’s famous work “An Experiment on a bird in the Air Pump” (see above) was first exhibited in 1768 and is currently in the collection of the National Gallery in London. Rich in symbolism [1,2], the painting shows a group of people gathered around an air pump used to create a vacuum in a series of demonstrations. On the table supporting the pump, we see Magdeburg hemispheres, that cannot be pulled apart once a vacuum has been created between them, and several other objects that had been used earlier in the evening’s entertainment. As Judy Egerton [3] comments, such demonstrations were a feature of the times:

Popular interest in the wonders of science was growing, disseminated by travelling lecturers on pneumatics (the air pump), astronomy (the orrery), optics and other subjects.

Further elaboration is provided by Stephen Daniels [4]:

Wright’s image of the lecture alludes to the many demonstrations of natural philosophy to mixed audiences by itinerant lecturers, using cheaper, portable apparatus. Spectacular display was seen as crucial to securing the appeal of science, but there was concern, especially with audiences, which included women and children, of bedazzling rather than enlightening them, confusing serious demonstrations with conjuring tricks, lecturers with showmen. Wright’s painting, set in a private library, with expensive equipment, presents a carefully regulated spectacle, establishing a contrast with the more flamboyant, explicitly commercial performances of scientific knowledge in playhouses and coffee-houses.

The climactic experiment in the demonstration shown in the painting was the effect of a vacuum on a bird in a bell jar. So, let’s examine what is going on by suggesting answers to four questions: Why use a bird? Why this bird? What was happening to the bird? What does the scene symbolise?

Why use a bird?

We have always envied animals with the power of flight and birds are potent symbols of freedom. We keep them in cages and aviaries for our enjoyment, knowing that, if they escaped, we may never see them again. They also make calls to communicate with other birds and, we like to think, with us. Ideal subjects, then, for the experiment we are witnessing, as we see the importance of air for both sound transmission and for life.

Why this bird?

We are surprised to see that the bird in the bell jar is not a common British species, but a white cockatoo, identified in Diana Donald’s book [2] as a Tanimbar cockatoo (also known as Goffin’s cockatoo). They are small members of the family and are native to what is now Indonesia and, at the time of Wright’s painting, were kept as pets. They are said to be affectionate towards humans [5] and some are known to talk well, in addition to making a lot of noise. Goffin’s cockatoos can thus be regarded as the bird equivalent of Cavalier King Charles Spaniels and an earlier picture by Wright shows such a cockatoo kept as a pet (see below). This may be the same bird that acted as the model in “An Experiment on a bird in the Air Pump”.

Goffin’s cockatoos are long-lived (with a life span often exceeding 20 years) and this meant that they could be imported by sea, kept in cages, and fed on nuts of various kinds, including coconut. No doubt, there was also chance to train them to say some recognisable words during transit and one can imagine that they were prized as a result, especially as they develop close relationships with humans. It is not known when they first became popular, but a white cockatoo is shown in Mantegna’s “Madonna della Vittoria” (see below) painted in 1496, at the time when exploration of the East Indies by Europeans was beginning – it is tempting to suggest that another way in which these sought-after birds were imported was via the Silk Road, but that is speculation.

Clearly then, a very valuable bird and one that formed relationships with people, often over decades. If it was used in a real experiment there was the prospect that a valued, and valuable, pet would be killed and this adds to the impact of the scene.

What was happening to the bird?

The cockatoo was removed from its cage and placed into the bell jar. This constraint must have resulted in much flapping and squawking and this would have continued as the handle of the pump was turned to expel air. The noise of the bird would then be reduced to demonstrate that sound does not travel through a vacuum and its struggling would have subsided until we come to the moment represented in the painting. The handle is no longer being turned and most of the audience are wondering for how many minutes the bird will survive, with emotions running from disinterest, through fascination, to fear and anguish. I have suggested [1] that the candle illuminating the scene was then snuffed, with the moon shining through the open window to provide the only light. The experimenter then released the vacuum, the bird started to recover, and the candle was re-lit. No doubt, much discussion followed, with feelings of relief, and probably tears of joy among the youngest observers.

What does the scene in the painting symbolise?

In addition to being a summary of a scientific demonstration, the scene also requires us to think about life and death; the stare of the experimenter, and his outstretched arm, commanding our involvement. That the bird was a precious pet, and possibly able to mimic human words, made the drama even more heightened. What would our reaction be if we were one of those around the table? We are certainly being invited into the circle.

I take the moonlight to be an allusion to the Lunar Society, an informal group of doctors, businessmen, craftsmen and scientists who were important in the English Enlightenment and with whose members Wright was associated. The experimenter is thought to be John Whitehurst, a member of the Lunar Society, but many have noted the superficial resemblance to Isaac Newton in the famous 1689 portrait by Kneller. At the climactic moment of the experiment, the light of the moon (The Enlightenment) illuminates the scene and, when candlelight returns to the room, the cockatoo recovers showing the human ability to control destiny and the power of the Enlightenment in promoting a rational approach.

There is also religious symbolism in the painting and I would like to quote from my earlier post [1]:

A white bird, usually a dove, is used as a convention to represent the Holy Spirit and we know from St John’s Gospel; chapter 14 verse 16 that Christ tells his Disciples that, after He leaves them, they will be comforted by a counsellor, widely interpreted as being the Holy Spirit. In the original Greek, the counsellor is termed parakletos and, in Wright’s day, the term paraclete was a familiar term for the Holy Spirit. As a cockatoo is rather like a parakeet (a term known to be used from the 16th Century), and can mimic human speech, is it too much of a stretch in imagination to think that we are looking at the symbolic threat to the idea of the Holy Spirit by the discoveries of scientific experiments?

So, we have a powerful, arresting image painted on a large scale and which demands questions from us. As Winged Geographers, our interest lies with the bird, but we are left with many questions about the scene – and what it all means. It is a great work of art.


[2] Diana Donald (2007) Picturing Animals in Britain 1750-1850. New Haven, Yale University Press.

[3] Judy Egerton (1990) Wright of Derby. London, Tate Gallery Publications.

[4] Stephen Daniels (1999) Joseph Wright. London, Tate Gallery Publications.


I am grateful to Michael Guida for his encouragement and for many helpful suggestions on how to improve an earlier version of this post.

Locations of illustrations:,_1768.jpg

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