Phosphorescent powder; 2 phials in box

Phosphorescence is a fascinating phenomenon. It is a mysterious light emitted by some substances after they are lit by light for a while. Until in the nineteenth century, its cause was a complete mystery. The phenomenon was investigated intensively. In one of the investigations, the time the substances continued to emit light, was measured. In 1768 John Canton made a powder of flowers of sulphur and oyster shells, which he called ‘Mr Cantons phosphorus’. The evacuated tubes shown here, are filled with this powder, which has a strong phosphorescent power. Because there are two tubes, comparative research can be carried out. For example: one of the experiments with such powder, described by John Canton, shows that heat releases the stored light faster. [See also the Luminescence Room.]