the balance center, the line
AA′
being the line of centers; the angle
WAA
equals half the total motion of the fork, the other half, of course, taking place on the opposite side of the center line.
WA
is the center of the fork when it rests against the bank. The angle
AA′X
represents half the impulse angle; the other half, the same as with the fork, is struck on the other side of the center line. At the point of intersection of these angles we will draw
cc