History

Melchisédech Thévenot, a French scientist, invented the instrument some time before February 2, 1661.This date can be established from Thevenot's correspondence with scientist Christiaan Huygens. Within a year of this date the inventor circulated details of his invention to others, including Robert Hooke in London and Vincenzo Viviani in Florence. It is occasionally argued that these bubble levels did not come into widespread use until the beginning of the eighteenth century, the earliest surviving examples being from that time, but Adrien Auzout had recommended that the Académie Royale des Sciences take "levels of the Thevenot type" on its expedition to Madagascar in 1666 It is very likely that these levels were in use in France and elsewhere long before the turn of the century.

Thevenot is often confused with his nephew, the traveler Jean de Thevenot (born 1633; died 1667). There is evidence to suggest that both Huygens and Hooke later laid claim to the invention, although only within their own countries

The Fell All-Way precision level, one of the first successful American made bull's eye levels for machine tool use, was invented by William B. Fell, Rockford, Illinois prior to WWII in 1939.The device was unique in that it could be placed on a machine bed and show tilt on the x-y axes simultaneously; eliminating the need to rotate the level 90 degrees.The level was so accurate it was restricted from export during World War II.The device set a new standard of .0005 inches per foot resolution (five ten thousands per foot or five arc seconds tilt).The level's production stopped around 1970. Production restarted in the 1980s by Thomas Butler Technology, Rockford, Illinois, but finally ended in the mid 1990s. However, there are still hundreds of the highly prized devices in existence.