A travelling scientist is shown demonstrating the formation of a vacuum by withdrawing air from a flask containing a white cockatoo, though common birds like sparrows would normally have been used. Air pumps were developed in the 17th century and were relatively familiar by Wright's day. The artist's subject is not scientific invention, but a human drama in a night-time setting.
The bird will die if the demonstrator continues to deprive it of oxygen, and Wright leaves us in doubt as to whether or not the cockatoo will be reprieved. The painting reveals a wide range of individual reactions, from the frightened children, through the reflective philosopher, the excited interest of the youth on the left, to the indifferent young lovers concerned only with each other.
The figures are dramatically lit by a single candle, while in the window the moon appears. On the table in front of the candle is a glass containing a skull.
From The National Gallery Podcast: Episode Nineteen, May 2008