This improved class of hooks are provided with a much deeper cavity than
those first introduced, an arrangement permitting of the employment of a
more commodious bobbin, which is generally covered by a cap, as in the
revolving shuttle, but free to revolve. In some cases the cap carries a
tension plate preventing its revolution with the hook. But beyond these
improvements on Wilson's original device, the utility of the hook mainly
depends upon two things quite apart from the hook itself. These are the
dispensing with the old fashioned check brush and the use of a positive
take-up.

Thus, in the original machine, the stitch was pulled up by the succeeding
revolution of the hook. For while one revolution sufficed to cast it over
the spool, a second turn was requisite to complete the stitch. In this way,
to make a first stitch with such an apparatus required two turns of the
rotating hook. The improvements mentioned enable the machine to complete a
stitch with one turn of the hook--an important step in advance, when we
consider that by the old method each length of slack thread must be
tightened up solely through the fabric and the needle eye. But this
particular arrangement bears so much upon the introduction of the positive
take-up itself that further reference to it must be reserved until that
device has been described.

_Simple Thread Hooks_.--The best known of these is Willcox & Gibbs. It has
been so often described, that no further reference to it may be made. It
continues to make the same excellent twisted stitch as it produced
twenty-five years ago.

_Of Vibrating Shuttles_.--These are shuttles of the long description,
moving in a segment of a circle. There are several varieties. The most