A balance wheel is a finely balanced disk that rotates fully one way and then the other, repeating the cycle over and over [see illustration on page 81].

• 所谓平衡齿轮是一个精细平衡的圆盘，可以正向反向来回旋转摆动（参见〈早期时钟机械原理的发展?4〉）。