that the slightly increased cost of the thread thus wound is the only
present bar to the extensive introduction of ready wound "cops."

_Of Thread Controllers_.--One of the earliest difficulties encountered by
the maker of a sewing machine was that of effectually controlling the loose
thread after it had been cast off the shuttle. In some machines this slack
thread amounts to six, in others to one or two inches. Howe got over the
difficulty by passing his thread, on its way to the needle, over the upper
extremity of the needle bar--the ascent of the bar, then, sufficed to pull
up the slack. Singer improved upon this by furnishing his machine with a
spring take-up lever, partially controlled by the needle bar.

[Illustration: FIG. 4.]

Wilson, in the Wheeler-Wilson machine, had neither of those arrangements,
but depended upon the succeeding revolution of the hook to draw up the
slack of the preceding stitch. These devices were all far from perfect in
their operation, chiefly because they commenced to act too soon. In each
case the pulling up commenced with the rise of the needle, and the
tightening operation subjected the thread to all the friction of rubbing
its way through both needle eye and fabric. Now, an ideal take-up should
not commence to act until the needle has ascended above the fabric, and one
of the most important steps toward perfection in sewing machines was
undoubtedly attained when such a device was actually invented. In effecting
this, the means employed consists of a differential or variable cam,
rotating with the main shaft. This controls the movements of a lever called
the take-up, pivoted to the machine (Fig. 4). Not only has it been
possible by these means to control the tightening of the stitch, but the
paying out of the thread for enveloping the shuttle also, and both the
paying out and pulling up are actually effected after the needle has