relation to the crank being changed when the engine is reversed; two
strong lugs are bolted on the shaft, one driving the eccentric in one
direction, the other in the opposite, by acting against the reverse
faces of a projection from the side of The eccentric pulley.

The loose eccentric is of course a familiar arrangement in connection
with poppet valves, as well as for the purpose of reversing an engine
when driving a single slide valve. Its use in connection with the Meyer
cut-off valves, however, is believed to be new; and the reason for its
employment will be understood by the aid of Fig. 6.

For the purposes of this explanation we may neglect the angular
vibrations of the connecting rod and eccentric rod, considering them
both as of infinite length. Let O be the center of the shaft; let L O M
represent the face of the main valve seat, in which is shown the port
leading to the cylinder; and let A be the edge of the main valve, at the
beginning of a stroke of the piston. It will then be apparent that the
center of the eccentric must at that instant be at the point, C, if the
engine turn to the left, as shown by the arrow, and at G, if the
rotation be in the opposite direction; C and G then may be taken as the
centers of the "go-ahead" and the "backing" eccentrics respectively,
which operate the main valve through the intervention of the link.

Now, in each revolution of the engine, the cut-off eccentric in effect
revolves in the same direction about the center of the main eccentric.
Consequently, we may let R C S, parallel to L O M, represent the face of
the cut-off valve seat, or, in other words, the back of the main valve,
in which the port, C N, corresponds to one of those shown in Fig. 4; and
the motion of the cut-off valve over this seat will be precisely, the
same as though it were driven directly by an eccentric revolving around