This paper gives an explicit description of the difference between the naive and canonical heights on the Jacobian of a curve of genus two defined over the rationals. Thus solving a known defect in a prior paper of E. V. Flynn and N. P. Smart [Acta Arith. 79, 333-352 (1997; Zbl 0895.11026)]. The author corrects the values for height constant in the previous paper and describes how the work extends to number fields. He then describes how one can find the rational torsion in the Jacobian. The paper includes a number of worked exampled and detailed formulae.