But many ingenious machinists have pondered long over the problem, and several clever contrivances have been invented with a view to its solution.  It may scarcely be necessary to say that the best manufacturers of sewing machines have conducted experiments with the same object in view, and the result has always been a return to the shuttle, with its steel bobbins.

Why is this, and how is it that a very big shuttle cannot be used, large enough, indeed, to accommodate any bobbin within itself?  The answer is very simple.  It has been done over and over again.

Since the whole bulk of the under thread must pass through the loop of the upper one, it, is quite clear that the size of that loop must be proportioned to the bulk of the shuttle.  Thus, a small shuttle would, perhaps, be covered by an inch of thread, while our supposed mammoth shuttle might require ten times that amount.  Now, let us consider that to sew an inch of thread into lock stitches frequently involves its being drawn up and down through both needle and fabric twenty times.  This means considerable chafing, and possible injury to the thread.

But if we were to sanction the use of capacious shuttles, ten inches of thread must undergo this chafing and seesaw treatment, and under the above conditions every part of the ten inches must pass up and down two hundred times—­treatment that might reasonably be expected to leave little “life” in the thread.  But in spite of this tremendous drawback, there are machines offered for sale made with such shuttles.

For reasons that I have now pointed out, it is quite clear that a large shuttle or bobbin is by no means an unmixed advantage.  Indeed, the very best makers of sewing machines have always striven to keep down the bulk of the shuttle, and in those splendid machines shown here to-night the use of the small shuttles is conspicuous.  It may be contended that small bobbins frequently require refilling, which is quite true, but the saving of the thread effected thereby, not to mention that of the machine itself, amply compensates for the use of small shuttles.  Apart from this, however, it is no longer necessary to wind bobbins at all.  Dewhurst & Sons, of Skipton, and Clark & Co., of Paisley, have produced ready wound “cops” or bobbins of thread for placing direct into shuttles.  Thus no winding of bobbins is necessary, and indeed the bobbins themselves are dispensed with.  I believe 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.