Some of the paintings by Joseph Wright of Derby, which are renowned for their use of light and shade, are of Lunar Society members. The Derby Gallery possesses over 300 sketches and 34 oil paintings by Wright, and also holds a document collection. One of the paintings is entitled "The Alchymist in Search of the Philosopher's Stone" (1771) and it depicts the discovery of the element phosphorus by German alchemist Hennig Brand in 1669. A flask into which a large quantity of urine has been boiled down is seen bursting into light as the phosphorus, which is abundant in urine, ignites spontaneously in air.