The painting departed from convention of the time by depicting a scientific subject in the reverential manner formerly reserved for scenes of historical or religious significance.

Boyle, the son of the Earl of Cork, had no such concerns—after its construction, he donated the initial 1659 model to the Royal Society and had a further two redesigned machines built for his personal use.

Many demonstrations could only be performed with Hooke on hand, and Boyle frequently left critical public displays solely to Hooke—whose dramatic flair matched his technical skill.

In this attempt to discover something "about the account upon which Respiration is so necessary to the Animals, that Nature hath furnish'd with Lungs", Boyle conducted numerous trials during which he placed a large variety of different creatures, including birds, mice, eels, snails and flies, in the vessel of the pump and studied their reactions as the air was removed.

[5] These were performed in town halls and other large buildings for a ticket-buying audience, or were booked by societies or for private showings in the homes of the well-off, the setting suggested in both of Wright's demonstration pieces.

[6] One of the most notable and respectable of the travelling lecturers was James Ferguson FRS, a Scottish astronomer and probable acquaintance of Joseph Wright (both were friends of John Whitehurst).

Ferguson noted that a "lungs-glass" with a small air-filled bladder inside was often used in place of the animal, as using a living creature was "too shocking to every spectator who has the least degree of humanity".

Wright's first attempt, A Girl reading a Letter by candlelight with a Young Man looking over her shoulder from 1762 or 1763, is a trial in the genre, and is fetching though uncomplicated.

However Judy Egerton wonders if he could have seen any, preferring as influences the far smaller works of the Leiden fijnschilder Godfried Schalcken (1643–1706), whose reputation was much greater in the early 18th century than subsequently.

Some of Wright's own later candlelit scenes were by no means as serious as his first ones, as seen from their titles: Two Boys Fighting Over a Bladder and Two Girls Dressing a Kitten by Candlelight.

But there seems no reason other than heightened drama to stage the air pump experiment in a room lit by a single candle, and in two later paintings of the subject by Charles-Amédée-Philippe van Loo the lighting is normal.

In some respects the Orrery and Air Pump subjects resembled conversation pieces, then largely a form of middle-class portraiture, though soon to be given new status when Johann Zoffany began to paint the royal family in about 1766.

[16] The 20th-century art historian Ellis Waterhouse compares these two works to the "genre serieux" of contemporary French drama, as defined by Denis Diderot and Pierre Beaumarchais, a view endorsed by Egerton.

The painting, which measures 72 by 94½ inches (183 by 244 cm), shows a grey cockatiel fluttering in panic as the air is slowly withdrawn from the vessel by the pump.

The witnesses display various emotions: one of the girls worriedly watches the fate of the bird, while the other is too upset to observe and is comforted by her father; two gentlemen (one of them dispassionately timing the experiment) and a boy look on with interest, while the young lovers to the left of the painting are absorbed only in each other.

[20] The scientist himself looks directly out of the picture, as if challenging the viewer to judge whether the pumping should continue, killing the bird, or whether the air should be replaced and the cockatiel saved.

[21] David Solkin suggests that little sympathy is directed toward the bird; the subjects of the painting show the dispassionate detachment of the evolving scientific society.

[26] Wright, who took many of his subjects from English poetry, probably knew the following passage from "The Wanderer" (1729) by Richard Savage:[27] The cockatiel would have been a rare bird at the time, "and one whose life would never in reality have been risked in an experiment such as this".

[29] In selecting such a rarity for this scientific sacrifice, Wright not only chose a more dramatic subject than the "lungs-glass", but was perhaps making a statement about the values of society in the Age of Enlightenment.

[7] The grey plumage of the cockatiel also shows much more effectively in the darkened room than the small dull-coloured bird in Wright's early oil sketch.

The young lovers may have been based on Thomas Coltman and Mary Barlow, friends of Wright's, whom he later painted in Mr and Mrs Thomas Coltman (also in the National Gallery) after their marriage in 1769; Erasmus Darwin has been suggested as the man timing the experiment on the left of the table, and John Warltire, whom Darwin had invited to help with some air pump experiments in real life, as the natural philosopher;[35] but Wright never identified any of the subjects or suggested they were based on real people.

Particularly striking is the similarity between Frye's mezzotint Portrait of a Young Man of 1760–1761 and the figure of the boy with his head cocked staring intently at the bird.

Wright's provincial status and ties to the Lunar Society, a group of prominent industrialists, scientists and intellectuals who met regularly in Birmingham between 1765 and 1813, have been highlighted, as well as his close association with and sympathy for the advances made in the burgeoning Industrial Revolution.

Shelagh Stephenson's play An Experiment with an Air Pump, inspired by the painting, was the joint winner of the 1997 Margaret Ramsay Award and had its premiere at the Royal Exchange Theatre, Manchester, in 1998.