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
Light crude oil on practical grounds than theoretical. The New York Mercantile Exchange (NYMEX) defines light crude oil for domestic U.S. oil as having an API gravity between 37° API (840 kg/m) and 42° API (816 kg/m), while it defines light crude oil for non-U.S. oil as being between 32° API (865 kg/m) and 42° API (816 kg/m). The National Energy Board of Canada defines light crude oil as having a density less than 875.7 kg/m (API gravity greater than 30.1° API). The government of Alberta, which produces most of the oil in Canada, disagrees and defines it as oil with a density