Visible escapement

I have been working on this fine French 19th century slate and marble clock today. It has a visible escapement which a nice deceptive feature on some of these clocks. The pallets are usually red jewels but this one has steel ones that interrupt the escape wheel. So it is time for another horology lesson. The escapement is at the end of the train of gears leading up from the mainspring power source. Its function is to drip out the power, otherwise the gear train would just race away. A clock's tick is the sound of the gear train stopping as the escapement locks. As one tooth unlocks the other pallet catches a tooth. The tooth gives impulse to the semi cylindrical pallet and this energy is transferred to the pendulum which keeps swinging and regulates the timekeeping of the clock.
There are several different escapements but this one was invented by Louis-Gabriel Brocot. The pallets are made from cylindrical pins of cornelian or steel. The diameter is slightly less than the distance apart of two escape-wheel teeth, the non-acting half of each pallet being cut away to give clearance. The locking is against the highest point of each semicircular pallet face. Impulse is given on the quarter-circular face from the highest point to the lower lip of the pallet. The escapement can be made dead-beat by cutting the locking faces of the escape wheel tangential to a circle drawn about the axis of the pallet staff, or the escapement may be made with slight recoil by cutting the escape-wheel teeth radial to its axis.