Electric light by the first practical electric arc light in 1806. By the 1870s, Davy's arc lamp had been successfully commercialized, and was used to light many public spaces. The development of a steadily glowing filament suitable for interior lighting took longer, but by the early twentieth century inventors had successfully developed options, replacing the arc light with incandescents. The energy efficiency of electric lighting has increased radically since the first demonstration of arc lamps and the incandescent light bulb of the 19th century. Modern electric light sources come in a profusion of types and sizes adapted to many applications. Most modern
President of the Royal Astronomical Society William Herschel in 1821, though he never chaired a meeting. Since then the post has been held by many distinguished astronomers. The post has generally had a term of office of two years, but some holders resigned after one year e.g. due to poor health. Francis Baily and George Airy were elected a record of four times each. Baily's eight years in the role are a record (Airy served for seven). Since 1876 no-one has served for more than two years in total. President of the Royal Astronomical Society The President of the Royal Astronomical Society (prior to 1831 known