‘An Experiment on a Bird in the Air Pump’ hangs in London’s National Gallery. Painted in 1768 by Joseph Wright ‘of Derby’, it is extraordinary, luminous. I try to creep up on it, so as to take its figures by surprise. They are gathered around a glass jar. It contains a parakeet, whose life is being brought to a premature and unpleasant end by the extraction of air from the chamber. Light spills out of the painting, catching the faces of the onlookers in movement; we cannot see the source, for it is obscured by what appears to be a brain in a vat of liquid. Two boys concentrate on the experiment, while the young couple to the left have little interest in the wretched bird. A man, an enthusiast, wild haired, wrapped in a red dressing gown and a shirt open at the neck, is pointing to the jar and declaiming to the watching boys. His other hand hovers above the brass mechanism and winding handle of the air pump, a precision instrument of its time, set in a heavy, ornate, wooden frame. Two young girls are visibly upset by the suffering; one covers her eyes with her hand while the other clutches her sister’s gown for support. Another man comforts the girls. He is pointing to the bird. We can imagine him saying: ‘Come now, this is science. Put away your childish sadness and take heed of our remarkable demonstration.’ Another boy, his face a mixture of malice and sorrow, is shutting up the birdcage hanging from the ceiling, while to the far right an older man rests his chin on his walking stick and stares at the apparatus with an unfocused, pensive gaze. Stepping back from the painting we can see the trappings of wealth: the rich finery of the clothes, the polished wood furniture and expensive apparatus, the heavy fresco plasterwork of a doorway in the background. The moon shines pale through a large sash window. It is a country house spectacle. These details are hidden in the half-darkness, away from the extraordinary chiaroscuro Wright achieves with the lamplight.