| | The Balance Wheel of a Watch - TimeZone |
 | | Having swung to a fully clockwise position, the balance wheel has "wound" the balance spring, and it is the force of the spring unwinding that reverses the direction of and propels the balance in the opposite direction, to the fully counter-clockwise position. |
 | | A compensation balance compensates for the effects of temperature on the balance spring (and does not, in contrast to common opinion, compensate for temperature effects on the wheel itself). |
 | | As a result, balance wheels are sometimes deliberately put out of poise to compensate for (non-temperature) errors introduced by the spring attachments (inner and outer) or spring overcoil (the last, top curve of the spring before attachment to the stud on the balance bridge). |
| www.timezone.com /library/horologium/horologium0013 (2300 words) |