VA
with the roller, will give us one-half the crescent, the remaining half being transferred to the opposite side of the line
A′ A2
. We will notice that the guard point has entered the crescent 1¼° before the fork begins to move.
The angle of opening for the crescent in the double roller escapement is greater than in the single, because it is placed closer to the balance center, and the guard point or dart further from the pallet center, causing a greater intersection; also the velocity of the guard point has increased, while that of the safety roller has decreased. [Fig. 24], at
ff
, shows the path of the dart
h
, which also has 1¼° freedom between bank and roller. From the balance center we draw
A′