'Sir James Dewar Lecturing on Liquid Hydrogen at the Royal Institution', 1904 by Henry Jamyn Brooks.
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, Henry Jamyn Brooks, 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.
These lectures, known as the Friday Evening Discourses were a stage for scientists to show their latest research and were usually loaded with demonstrations. The apparatus would all be set up on the bench before the lecture and the lecturer would come to each experiment in turn. Huge sheets of calico with relevant diagrams helped the audience follow the thread of the lecture.
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.
Brooks included so many famous people in the audience of this painting that we couldn't possibly tag them all. If you'd like to see who else is depicted you can download a full list, along with a numbered image key, on the right.
Fancy joining the audience yourself? Find out what's on at the Ri, from exciting family events, to historic Friday Evening Discourses.