A large brass miner's dial and inclinometer with an attachment for a surveyors tripod. It was made by John Davies & Son of Derby in the late 19th century.
The miner's dial was used by a surveyor to establish the direction in which the mine's underground roadways and tunnels went. The inclinometer on this instrument also allows the surveyor to record the angles at which mine tunnels descend into the ground. The Coal Mines Act of 1911 made it compulsory for mine owners to keep records of where their mines were sunk, and it was a mine surveyor's job to make these detailed plans of colliery sites.
The science of surveying has always played an important role in the history of mining. The Ancient Egyptians were some of the first people to make use of surveying, employing it in the excavation of their gold mines from around 1400 BC.