disk has found most favor. In many cases two of these plates, fast and
loose, are placed upon the main shaft, and their separation and contact
controlled by the treadle. The great sensitiveness of the friction
attachment employed by the Singer company is due chiefly to the
transference of the friction plates to the axis of the machine itself (Fig.
13). Their contact and separation are controlled by a lever worked by a
very slight movement of the treadle. But the chief point of interest in
this device lies in the combination with the lever of a brake, enabling the
operator, by a simple reversal of the treadle's motion, to instantly
suspend the rotation of the machine. The forked lever, in fact, acts
simultaneously in throwing off the motion and applying the brake. The speed
is always in direct proportion to the pressure exerted upon the treadle,
and a single stitch can be made at will. Fig. 14 shows the friction wheel
separated, the portion a being fast, and e loose.

[Illustration: FIG. 13.]

[Illustration: FIG. 14.]

The Wheeler & Wilson company do not confine themselves to any particular
controller, but prefer the form shown here this evening (Fig. 15), in which
two bands and an intermediate pulley are employed. The first band is left
rather loose, and the machine is set in motion by the tightening of this
band through the depression of the treadle. The speed varies in proportion
to the pressure applied, and the sensitiveness of the arrangement is
increased by a brake device coming into play by the reversal of the treadle
as before.

[Illustration: FIG. 15.]