worm and sector. The
distance, JO, in Fig. 10, or in other words the length of the lever, M,
is precisely equal to the distance, AB, in Fig. 7, measured in a right
line; and the rods, R and S, from center to center of the eyes, are also
each of precisely this same length. Further, the axis about which the
reversing lever, T, vibrates is so situated that when that lever, as in
Fig 11, is thrown full to the left, the pin in its upper end is exactly
in line with the rock-shaft, O.

When the parts are in this position, the suspension-rod, S, the arm, G,
and the lever, M, will be as one piece, and their motions will be
identical, consisting simply of vibration about the axis of the
rock-shaft, O. The motion of the lever, M, is then due solely to the
pin, B, which is in this case exactly in line with the journal, J, so
that the result is the same as though this eccentric rod were connected
directly to the lever; and the pin, P, being also in line with B and J,
and kept so by the suspension-rod, S, it will be seen that the
bridle-rod, R, will move with the link, L, as though the two were
rigidly fastened together.

When the reversing lever, T, is thrown full to the right, as in Fig. 12,
the pin, P, is drawn to the inner end of the slot in the arm, G, and is
thus exactly in line with the rock-shaft, O. The suspension-rod, S,
will, therefore, be at rest; but the pin, A, will have been drawn, by
the bridle-rod, R, into line with the journal, J, and the bridle-rod
itself will now vibrate with the lever, M, whose sole motion will be
derived from the pin, A.

There is, then, no block slip whatever when the link thus suspended and
operated is run in "full gear," either forward or backward.

If this arrangement be used in cases where the link is used as an
expansion device, there will be, of course, some block slip while
running in the intermediate gears. But even then, it is to be observed
that the motion of the pin, A, relatively to the rocker arm is one of
vibration about the moving center, J; and its motion relatively to the
sliding block, E, is one of vibration about the center, P, whose motion
relatively to E is a small amount of sliding in the direction of the
slot, due to the fact that the rocker arm itself, which virtually
carries the block, E, vibrates about O, while the suspension-rod, S,
vibrates about another fixed center. It will thus be seen that, finally,
the block slip will be determined by the difference in curva