One of George Daniels's central contributions to horology is his co-axial escapement. Having observed that the dominant lever escapement begins to change its rate after a year or two -- a disturbance caused by the sliding action of the impulse elements of the escapement -- Daniels set about developing a mechanism that avoided this problem. The result of his efforts was the co-axial escapement, a mechanism in which he sought to combine the strengths and eliminate the deficiencies of existing watch escapements, the lever escapement foremost among them. First devised in 1977, today it remains largely the same as fitted in watches of Daniels's own manufacture, as well as those of several wrist-watch manufacturers. This book explains the action of the escapement in terms accessible to both expert and layman, and is accompanied by a series of detailed line drawings.