Spirit level

A spirit level is an instrument designed to indicate the level of a surface. Most commonly spirit levels are employed to indicate how horizontal or how vertical a surface is. Often also a indicator for a 45 degree inclination is included. Some are also capable of indicating the level of a surface between horizontal and vertical to the nearest degree. .

Spirit levels feature a slightly curved glass tube which is incompletely filled with a liquid, leaving a bubble in the tube.

The name "spirit level" has its origin in the use of spirits (eg. wine) in the glass tube.

The crudest form of the spirit level is a circular flat-bottomed device with the liquid under a slightly convex glass face which indicates the center clearly.

Its invention is credited to either Jean de Mechisedech Thevenot or Robert Hooke^[1]. Those attributing the invention to Jean de Thevenot date it in the range of 1662^[1] to 1666^[1].