John Hartnup was Superintendant of the Liverpool Museum, in the course of his work he tested many chronometers and was acutely aware of middle temperature error. Seeking a solution to the problem, he designed this balance in about 1847 with the assistance of the Liverpool chronometer maker Charles Shepherd. Hartnup refused to patent his balance, in fact he publicised it widely for the benefit of the trade. However, in the hands of other makers, it did not do as well as for those fitted to Shepherd's chronometers.