The sinumbra (or 'without shadow') lamp was patented in 1809. Oil is contained in the hollow circlet which also supports a glass shade. the oil subsequently passes down tubes from the circlet to a burner below. This design overcame the problem of shadows cast by the reservoir of the previously used Argand lamp. See Bourne and Brett Lighting in the Domestic Interior, Sotheby's Publications 1991, p.172.