These clocks were mostly made in the 17th century. The movement was housed in a drum-shaped canister that rolled down a slope; rewinding was effected by placing the clock at the top of the slope again. Sometimes the edges of the slope were marked off in seven-day intervals so the position of the clock could also indicate the day of the week. The clock mechanism contained a heavy weight which, in association with wheel train and escapement, controlled the tendency of the clock to roll down the slope. The time was indicated by a fixed single hand, kept in equilibrium by the weight of the mechanism and the heavy weight working against each other. The idea appears to have been revived by a Dutchman named Isaac Jones Drielsma, working in Liverpool c. 1835, but his plans for producing the clocks in quantity were not fulfilled.