Wire from Finsen ultraviolet lamp for red fabric, presented by Princess Alexandra to the London Hospital in 1900

This Finsen lamp was presented to the Royal London Hospital (formerly the London Hospital) by Queen Alexandra (1844-1925) when she was Princess of Wales. The lamp was named after its inventor, Neils Ryberg Finsen (1860-1904), who in 1894 pioneered the use of ultraviolet light (UV) to treat tuberculosis of the skin. The UV light is projected through each of the four telescopes so four patients can be treated at once. This type of treatment declined with the introduction of antibiotics but a lamp was kept in case the drugs did not work. The Finsen lamp was also used to treat rickets from the 1920s onwards.