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
Royal Society of Thailand is on a par with weapon" (ปัญญาประดุจดังอาวุธ). The light of the sword represents the light of wisdom. The crown represents the monarch. Perhaps the most well-known work of the society is the prescriptive "Royal Institute Dictionary" (พจนานุกรม ฉบับราชบัณฑิตยสถาน, in English often abbreviated RID). The society has published four fully revised editions of the dictionary, and many intermittent reprintings with minor revisions. Each of the major revisions is associated with a significant year in Thai history, although in the case of the 1999 and 2011 editions, the actual publication date is a later year. The Royal Society publishes guidelines for spelling