The lengths of the links comply with the conditions: A͞B=D͞C and A͞D=B͞C. Thus the basic mechanism of the balance is a parallel-crank linkage ABCD. When pan c of the balance descends, link 1 actuates shaped lever 4 which rolls along flat surface 2 and carries hand 3. Dial scale a requires special graduation. Weight b counterbalances the weights of the pan and the links of the mechanism.
$788$LW,B$