This image depicts a formal lecture to Members of the Royal Institution by James Dewar. The audience includes many famous people from science, industry and politics including Lord Rayleigh, Lord Kelvin and Arthur Balfour, the Prime Minister of the time. While supposedly depicting an actual event, the artist wanted to make sure that he did not leave anyone important out, whether or not they were really there or even alive at the time.

Dewar was famous for being the first person to liquefy hydrogen by cooling it to −252.87°C. It was a dangerous process: Robert Lennox, one of his assistants, was caught in an explosion and lost an eye. You can see him in the background, turned away from the viewer to hide the scars. Dewar also invented the vacuum (thermos) flask to minimise heat loss and so keep gas liquid for as long as possible.