At starting out, we will first agree on the names of the several parts of this escapement, and to aid us in this we will refer to the accompanying drawings, in which Fig. 122 is a side elevation of a cylinder complete and ready to have a balance staked on to it.  Fig. 123 shows the cylinder removed from the balance collet.  Figs. 124 and 125 show the upper and lower plugs removed from the cylinder.  Fig. 126 is a horizontal section of Fig. 122 on the line i.  Fig. 127 is a side view of one tooth of a cylinder escape wheel as if seen in the direction of the arrow f in Fig. 126.  Fig. 128 is a top view of two teeth of a cylinder escape wheel.  The names of the several parts usually employed are as follows: 

A.—­Upper or Main Shell.
A’.—­Half Shell.
A’’.—­Column.
A’’’.—­Small Shell.
B B’ B’’.—­Balance Collet.
G.—­Upper Plug.
H.—­Lower Plug.
g.—­Entrance Lip of Cylinder.
h.—­Exit Lip of Cylinder.
c.—­Banking Slot.
C.—­Tooth.
D.—­U arm.
E.—­Stalk of Pillar.
I.—­U space.
l.—­Point of Tooth.
k.—­Heel of Tooth.

The cylinder escapement has two engagements or actions, during the passage of each tooth; that is, one on the outside of the cylinder and one on the inside of the shell.  As we shall show later on, the cylinder escapement is the only positively dead-beat escapement in use, all others, even the duplex, having a slight recoil during the process of escaping.

When the tooth of a cylinder escape wheel while performing its functions, strikes the cylinder shell, it rests dead on the outer or inner surface of the half shell until the action of the balance spring has brought the lip of the cylinder so that the impulse face of the tooth commences to impart motion or power to the balance.

[Illustration:  Fig. 122]

[Illustration:  Fig. 123]

[Illustration:  Fig. 124]

[Illustration:  Fig. 125]

[Illustration:  Fig. 126]

[Illustration:  Fig. 127]

[Illustration:  Fig. 128]

Most writers on horological matters term this act the “lift,” which name was no doubt acquired when escapements were chiefly confined to pendulum clocks.  Very little thought on the matter will show any person who inspects Fig. 126 that if the tooth C is released or escapes from the inside of the half shell of the cylinder A, said cylinder must turn or revolve a little in the direction of the arrow j, and also that the next succeeding tooth of the escape wheel will engage the cylinder on the outside of the half shell, falling on the dead or neutral portion of said cylinder, to rest until the hairspring causes the cylinder to turn in the opposite direction and permitting the tooth now resting on the outside of the cylinder to assume the position shown on the drawing.