'Student' lamp, c 1830.
© Science Museum / Science & Society Picture Library
The lamp could be adjusted in height to suit the user and included a green shade to reduce glare. Variations on this reading lamp design continued to be produced throughout the 19th century. Fuelled by colza (rapeseed) oil, the lamp's reservoir was higher than the wick, and the oil, which was viscous like modern cooking oil, flowed down under gravity. A series of metal float valves faced with cork determined and controlled the amount of air and oil flowing in and out of the reservoir, preventing a vacuum effect.