Finsen's Lens for Sun's Rays, photograph.
Finsen's Lens for Sun's Rays, photograph.
A system of instruction in X-ray methods and medical uses of light, hot-air, vibration and high-frequency currents : prepared especially for the post-graduate home study of surgeons, general physicians, dentists [etc.] / by S. H. Monell. New York : E. R. Pelton, [c1902]. M742247s 1902 Osler - Robertson.
Finsen explained that he began experimenting with phototherapy with natural sunlight through glass, but after realizing that UV rays cannot pass through ordinary glass, he switched to quartz lens. This photograph depicts a lens of Finsen's design, used to direct the sun's rays.
