Perhaps it would be as well to give a general description of the model before taking up the details.  A reduced side view of the complete model is given at Fig. 26.  In this cut the escapement model shown at Figs. 24 and 25 is sketched in a rough way at R, while N shows a glass cover, and M a wooden base of polished oak or walnut.  This base is recessed on the lower side to receive an eight-day spring clock movement, which supplies the motive power for the model.  This base is recessed on top to receive the main plate A, Fig. 24, and also to hold the glass shade N in position.  The base M is 21/2” high and 8” diameter.  The glass cover N can have either a high and spherical top, as shown, or, as most people prefer, a flattened oval.

[Illustration:  Fig. 26]

The main plate A is of hard spring brass, 1/10” thick and 6” in diameter; in fact, a simple disk of the size named, with slightly rounded edges.  The top plate, shown at C, Figs. 24 and 25, is 1/8” thick and shaped as shown.  This plate (C) is supported on two pillars 1/2” in diameter and 11/4” high.  Fig. 25 is a side view of Fig. 24 seen in the direction of the arrow p.  The cock D is also of 1/8” spring brass shaped as shown, and attached by the screw f and steady pins s s to the top plate C.  The bridge F G carries the top pivots of escape wheel and pallet staff, and is shaped as shown at the full outline.  This bridge is supported on two pillars 1/2” high and 1/2” in diameter, one of which is shown at E, Fig. 25, and both at the dotted circles E E’, Fig. 24.

To lay out the lower plate we draw the line a a so it passes through the center of A at m.  At 1.3” from one edge of A we establish on the line a the point d, which locates the center of the escape wheel.  On the same line a at 1.15” from d we establish the point b, which represents the center of the pallet staff.  At the distance of 1.16” from b we establish the point c, which represents the center of the balance staff.  To locate the pillars H, which support the top plate C, we set the dividers at 2.58”, and from the center m sweep the arc n.

From the intersection of this arc with the line a (at r) we lay off on said arc n 2.1” and establish the points g g’, which locate the center of the pillars H H.  With the dividers set so one leg rests at the center m and the other leg at the point d, we sweep the arc t.  With the dividers set at 1.33” we establish on the arc t, from the point d, the points e e’, which locate the position of the pillars E E’.  The outside diameter of the balance B is 3-5/8” with the rim 3/16” wide and 5/16” deep, with screws in the rim in imitation of the ordinary compensation balance.