and as a basis from which
the improved results to be recorded should necessarily be shown to spring.

The essential feature of this valve gear is that movement for the valve is
produced by a combination of two motions at right angles to each other;
and by the various proportions in which these are combined, and by the
positions in which the moving parts are set with regard to each other, it
gives both the reversal of motion and the various degrees of expansion
required. Eccentrics are entirely dispensed with and the time-honored link
gear abandoned, the motion is taken direct from the connecting rod, and by
utilizing independently the backward and forward action of the rod, due to
the reciprocation of the piston, and combining this with the vibrating
action of the rod, a movement results which is suitable to work the valves
of engines, allowing the use of any proportions of lap and lead desired,
and giving an almost mathematically correct "cut-off" for both sides of
the piston and for all points of expansion intermediately, as well as a
much quicker action at the points of "cut-off" and "release" than is given
by a link gear.

The machinery for accomplishing this is both less costly and less
complicated than the ordinary link motion, and is shown in elevation on
cut, which is a view of the complete motion as on the first London and
North-Western locomotive. Here E is the main valve lever, pinned at D to a
link, B, one end of which is fastened to the connecting rod at A, and the
other end maintained in about the vertical by the radius rod, C, which is
fixed at the point, C. The center or fulcrum, F, of the lever, E,
partaking of the vibrating movement of the connecting rod at the point, A,
is carried in a curved slide, J, the radius of which is equal to the
length of the link, G, and the center of which is fixed to be concentric
with the fulcrum, F, of the lever when the piston is at either extreme end
of its stroke. From the upper end of the lever, E, the motion is carried
direct to the valve by the rod, G. It will be evident thus that by one
revolution of the crank the lower end of the lever, E, will have imparted
to it two different movements, one along the longer axis of the ellipse,
traveled by the point, A, and one through its minor axis up and down,
these movements differing as to time, and corresponding with the part of
the movement of the valve required for lap and lead, and that part
constituting the port open