For years the jail was erroneously thought to date from the late eighteenth century, but recent research has proved that the rear granite cell block dates from 1858. Cells for male prisoners, half underground, are narrow spaces with no more than a shelf for sleeping and a barred slot for light. A lightless cell at one end provided for solitary confinement. A single cold-water shower at the end of the corridor served all prisoners. On the floor above are cells for women prisoners, more like rooms, squarish in shape, each having a full sash window with view, and originally furnished with beds. The front block of the building was added in 1861 as a warden's residence. Today each of the cells provides a showcase for an aspect of eighteenth- or nineteenth-century life, with books and historical records in the front of the building.