Prisoners working at the tread-wheel, and others exercising, in the 3rd yard of the Vagrants' Prison, Coldbath Fields

Book illustration of prisoners working at the tread-wheel, and others exercising, in the 3rd yard of the Vagrants' Prison, Coldbath Fields, from page 307 of 'The criminal prisons of London and scenes of prison life' by Henry Mayhew and John Binny. The treadmill was invented by Mr Cubitt of Ipswich and the first example was introduced to Brixton prison in 1817. The prisoners referred to working the treadmill as "grinding the wind", a pointless activity whereby "the sole object of the labour of some 150 men, employed for eight hours a day, [is] simply to put in motion a big fan, or regulator, as it is called, which, impinging on the air as it revolves, serves to add to the severity of the work by increasing the resistance."

Coldbath Fields had six wheels, each containing 24 steps, with the wheel revolving twice a minute. After every 30th revolution (i.e. 15 minutes) a bell would ring the men would be relieved. "Every man put to labour at the wheel has to work for fifteen quarters of an hour every day." The authors condemn the use of such "degrading penal instruments" as the treadmill.