2018 marks the 250th Anniversary of Joseph Wright of Derby’s magnificent painting “Experiment on a Bird in the Air Pump” (see below) and, to understand its subject, we need to travel back in time to gain a brief impression of life in England in 1768. Transport was still mainly on rough roads and tracks, although a canal network was beginning to develop and the first canals were in operation. These enabled the transport of heavy loads and provided an effective means of distribution, both essential factors allowing the Industrial Revolution that was to begin in the 1780s. On the intellectual front, there was much interest in scientific discoveries, especially those by Newton, Boyle and Hooke in the latter half of the 17th Century, and Enlightenment groups met to discuss science and its role in the wider cultural world. It was a time of great intellectual excitement and the Lunar Circle, founded in 1765, was an important group of Enlightenment figures that maintained contact through active correspondence. The group became even more famous in 1775 as the Lunar Society, holding meetings in the Midlands each month, at the time of the full moon.
Joseph Wright was an associate of the Lunar Circle and was influenced strongly by the thinking of its members . He was born in 1734, the fourth child, and third son, of John Wright, an attorney in Derby; a profession that John had inherited from his father and which he passed on to this eldest son, also called John. Joseph’s father was nicknamed “Equity Wright” because of his fairness in the application of the law  and one can imagine that Joseph grew up in an atmosphere of considered values and where there was much discussion. It is also likely that music also played a part in family life, as Joseph became a competent flautist and music meant a good deal to him throughout his life. He had a passion for drawing and became fascinated by forges, what was made there and the play of light generated by the fire. Joseph also made models of guns and of “raree shows” (early peepshows)  that itinerant entertainers brought to the town.
Although clearly skilled with his hands, it was not clear what profession Joseph would follow, as his father was resistant to him becoming a professional artist. In later life, Joseph suffered from anxiety and depression , so we can imagine that he was a sensitive youth, keen to follow his passion for drawing and painting. John saw this and changed his view about his son’s future career, deciding that Joshua needed an expert teacher. He arranged for him to be apprenticed to Thomas Hudson in London in 1751 , who specialised in portraiture and ten years earlier had been the master of Joshua Reynolds.
From Hudson, Wright learned much about painting technique and he became an accomplished technical painter, carefully building up pictures on the canvas and ensuring that there was a good binding between layers . On returning to Derby, Joseph then began to take commissions for portraits (always popular among potential clients), returning to Hudson’s studio in 1756 to further polish his skills. Alongside his work as a portraitist, Joseph continued his interest in the effects of light on subjects and this reached its peak in the great painting that is the subject of this essay. In looking at light, he was strongly influenced by John Whitehurst FRS, a member of the Lunar Circle who lived in Derby. Whitehurst was a clock and instrument maker who had been recognised by the Royal Society and, from that august body, learned of Newton’s studies on optics and much else besides. Whitehurst was expert in his knowledge of the physical sciences and, being twenty years older than Joshua, was an authority figure to him. The other major influence on Joshua’s thinking was Erasmus Darwin , who was to move to Derby later in life, but who lived in Lichfield in the 1760s. Darwin was a physician (he treated Wright), but was also a poet and an accomplished natural historian. He was an early exponent of ideas on evolution, although these were sketchy.
With this background, let’s turn to “Experiment on a Bird in the Air Pump”. Of course, we cannot see the layering of the paint but we are certainly aware of a strong chiaroscuro, with illumination provided by a candle. We do not see the flame, nor, of course, do we see any flickering, but we are aware that the chiaroscuro provides an oval frame for the principal subject matter. The only objects outside this “frame” are the window, the boy holding the cage, the hand of the experimenter and (dimly) some features of the room in which the meeting is taking place. Our gaze is mainly concentrated within this oval frame and we whizz round the characters, from the experimenter to the others in the room, stopping to look at them before moving on. A separate “oval of illumination within the oval” highlights two girls and a gentleman and verticals within the composition draw us across to see other features. I have not seen any print-outs of eye movement trackers from those looking at Wright’s masterpiece, but I would imagine that they would be highly dynamic.
The subject of the painting is a travelling demonstration in which various Enlightenment topics were to be presented. I imagine that the show began with a discussion of optics and, especially, of refraction in fluids. Two jars have sticks in them (see details above) and we see clearly how these appear broken: the effect of the shape of a curved vessel on their appearance is also evident. While the jar that is closest to us also contains a cloudy fluid, and an object that is difficult to define, the jar to the right, which has had its cork removed, contains a stick that appears to be a cut-down quill. Drawing up liquid in the hollow quill, using it like a contemporary drinking straw, introduced the audience to the idea of the effect of lowered pressure on fluids and the power of atmospheric pressure. This led to one of the central themes of the painting – the use of an air pump. The one illustrated was probably designed by Hauksbee and consisted of two cylinders, each of which contained a piston. By turning the handle on the pump, a link caused the pistons to move up and down and, because valves were present, air was drawn out of any chamber to which the tube of the air pump was attached. Air pumps played a vital role in 17th Century science, leading to important demonstrations of the role of air in affecting the fall of objects (feathers falling at the same rate as coins); combustion (a lit taper becomes extinguished in a vacuum); and the effect of vacuum on sound, but not light (light passing through a vacuum but not sound).
The first experiment with the air pump was to demonstrate the power of atmospheric pressure using Magdeburg hemispheres. These are seen on the table (see above) and the demonstration began by holding the two hemispheres together while the tube from the air pump was attached to the side of the resultant sphere. A vacuum was then created and the tap of the connection closed so that it was maintained. It is probable that the evacuated sphere was then passed around the audience and no-one would have been able to pull the two hemispheres apart. On releasing the vacuum, the pressure equalised between the hemispheres and the surrounding air, and they could be separated easily, perhaps to the astonishment of some, but not all, of the audience.
The second experiment with the air pump was a demonstration of the effect of a lack of air on life – a biological experiment. I imagine that there was much discussion among the group about life and our failure to define it (something we still have difficulty with) and the subject of the experiment was a cockatoo that had been removed from its cage (above the boy on the right). The unfortunate bird was placed into the glass chamber and the experimenter’s assistant (who has his side to us, see above) began to turn the handle of the air pump. The first thing noticed by the audience would be that the squawking of the bird became less audible as the vacuum was formed and the cockatoo's panic became less as it began to suffocate. At this point, I imagine that the assistant, who was timing the experiment, used the snuffer in front of him to put out the candle flame and the room would then have darkened, to be lit only by moonlight. The experimenter then gently allowed air into the vessel (we see his hand poised on the valve before the candle is extinguished, see below), the candle was re-lit by means of a taper and there was much relief that the bird was able to recover and eventually be placed back in its cage. For a time, just before the candle was snuffed, it was not known what the result would be and the painting shows us the expressions of the audience at this moment of maximum tension. Let’s consider their reactions.
The experimenter strikes a dramatic pose that one would expect at the moment before the candle is snuffed. He challenges us by staring straight from the painting, with his hand outstretched. The person that I recognise as the experimenter’s assistant is focused on proceedings (as he needs to be) and seems dispassionate, while the boy to his left is focussed on the fate of the bird, with some anticipation and excitement. The gentleman at the bottom right is clearly contemplating death and he is fixed on the memento mori  provided by the skull-like, but amorphous, object in the jar at the front of the table. He has a walking stick with him, not an elegant cane, and we assume that he needs this for support and that he is feeling the effects of age. The couple at the left upper of the painting seem rather detached and one can imagine that they are a couple who are out for an evening’s entertainment, while mainly being interested in each other. One can almost imagine the man making a cheeky comment or two during proceedings and his thoughts may well have been on things other than the possible death of the bird: perhaps on events that result in new human lives coming into existence? In contrast to his apparent nonchalance, the two girls on the right show distress and anxiety at what is happening and they are being comforted by the gentleman who gives the impression that he has seen the experiment before and knows that the bird will not die. The linking of the girls’ arms, and the oval of light that bathes them, stresses the strength of their feelings; the hand around the shoulder of the elder girl provides reassurance. One might ask what young girls are doing at an evening of this kind, something that becomes clearer when the symbolism of the work is explored in the next part of this essay.
Thus far, we have taken the painting at face value, but it also reminds us of many Christian religious works. Let’s consider some of the imagery in the painting from this standpoint and think about how this links to Enlightenment thinking on the importance of science and of scientific experiments. The evening then becomes one of “worship”. The candle flame illuminates everything and this is a parallel to the Light of the World of Christianity. We now have an an explanation for the presence of the girls, as we know from Luke’s Gospel chapter 18 verse 16 that we should “suffer little children to come unto me”. This applies to the new knowledge in science, just as it does to the Christian religion, and the gentleman reassuring the girls thus has the role, and demeanour, of a cleric. The disinterested couple are so involved with themselves that neither religion or science is likely to touch them that evening and the elderly gentleman in the foreground knows that death is approaching, however we understand that event.
The experimenter has been identified as John Whitehurst , but the long grey hair and angular features bear a resemblance to the image of Sir Isaac Newton painted by Sir Godfrey Kneller in 1689. While this might be coincidental, it does make a connection in our minds. Newton was recognised in Wright’s time (and ours) as having made extraordinary advances in optics (the early part of the demonstration in the painting) and other branches of the physical sciences and mathematics and thus would have an almost theistic status among some Enlightenment thinkers. Although he was an egomaniac, this role would not have gone down well with Newton himself, as he was a Christian, even though years of intense scholarship resulted in doubts about some of the tenets of the Christian Church . Our experimenter certainly controls the life and death of the bird and his hand, at the uppermost part of the painting, is like the hand of God (see above).
The most important symbol in the painting is the cockatoo and one wonders whether such a bird would have been risked in the demonstration. Cockatoos come originally from what we now call Australasia and Indonesia and there are several species, the commonest of which is the sulphur-crested cockatoo. The bird in the painting lacks a yellow crest and appears to be the same bird that Wright had painted five years before in his portrait of Mr and Mrs Chase (see above). Cockatoos are known to live for many decades, even a hundred years being possible, and the bird in the experiment would have been a cherished pet. In addition to much squawking, cockatoos are also known to mimic sounds, including human voices, so it is probable that the bird in the experiment “talked” a few words (that is likely to have been understood by those observing the painting, even if its presence is an invention). It must have been rare and, no doubt, expensive, and hardly likely to be risked in a real experiment. White cockatoos were found in Europe in much earlier times and their long life may have allowed them to be traded along old trade routes like the Silk Road, having been obtained originally from people selling spices from southern Asia. Interestingly, the painting by Andrea Mantegna of “Madonna della Vittoria” sees the Virgin sitting in a bower that has birds sitting in the trellis-work. One of the these is clearly a white cockatoo – and this in a work from 1496 (see below, with detail).
The boy on the right of the illuminated group looks out, and up, from the painting and holds the rope of the empty cage. Like the rest of the audience, he wonders whether the bird will be returned and, at the moment the candle is snuffed, he will be brightly illuminated by the moonlight streaming through the window. This leads us further into the religious symbolism of the work. 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? Certainly, the moonlight suggests that the Lunar Circle and Enlightenment thinking had a part to play in asking this question. We know that Erasmus Darwin, a major influence on Wright, tended toward atheism  (although care is needed in interpreting that term) and perhaps his influence is being demonstrated here? We do not know whether Wright was a theist, but it is likely as he was probably a Freemason and Whitehurst, his mentor, was certainly an active Mason .
“Experiment on a Bird in the Air Pump” suggests that we are witnessing the beginnings of a conflict between science and religion in the late 1700s. The Christian Church held immense power for centuries up to the Enlightenment, but scientific discoveries and, even more importantly, their application to industrial processes, was having an effect on this power. Another jolt was to come 90 years after Wright’s painting when Charles Darwin (Erasmus Darwin’s grandson) published “The Origin of Species” in 1859. In the contemporary world, we have strongly materialist societies and the Christian religion is losing its significance (although other religions, each with their own moral code, are increasing their influence,). As Science moves to ever more mechanistic approaches – we are now threatened with Quantum Biology, for example – there is belief that this will provide more and more answers. For sure, there will be useful spin-offs, just like there have been from studies in genetics, but the demeaning of pure research as being “blue sky”, and the blind growth of mechanism looks to me to bear the threat of a new Dark Age. I wonder how Wright’s painting will be viewed in 250 years’ time? Perhaps theistic explanations will be favoured and those of science found wanting – the reverse of the position anticipated by Wright’s painting?
 William Bemrose (1885) The Life and Works of Joseph Wright, A.R.A., commonly called “Wright of Derby.” London, Bemrose and Sons
 Stephen Daniels (2002) Joseph Wright. London, Tate Gallery Publishing.
 Rica Jones (1990) Wright of Derby’s techniques of painting. In: Wright of Derby (ed. Judy Egerton). London, Tate Gallery Publishing.
 David Fraser (1990) Joseph Wright of Derby and the Lunar Society. In: Wright of Derby (ed. Judy Egerton). London, Tate Gallery Publishing.
 Richard Westfall (1993) The Life of Isaac Newton. Cambridge, Cambridge University Press.
I was invited to give a Lunchtime Talk on Joseph Wright of Derby’s “Experiment on a Bird in the Air Pump” at the National Gallery in London in October 2018. This essay provides the background to the talk and a flavour of its content.
For a larger image of the painting, see: https://en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump#/media/File:An_Experiment_on_a_Bird_in_an_Air_Pump_by_Joseph_Wright_of_Derby,_1768.jpg
I would like to thank Paul Ranford and Matthew Morgan for conversations that have influenced my ideas and Lucy Bamford for pointing out typographical errors in the original post..
For those wanting to know more about Joseph Wright, Stephen Daniels’ book  provides an excellent, and accessible, review of the artist and his influences.