eel is
dropped, and is free to revolve quite loosely. Variation of tension is thus
obviated in a very simple manner. The chief point of interest in the
machine is undoubtedly the means employed in transferring the motion from
the main shaft to the underneath parts, an arrangement as ingenious and
effective as any device ever introduced into stitching mechanism. It is the
invention of Mr. Robert Whitehall, and consists of a vertical rocking shaft
situated in the arm of the machine Motion is imparted to it by means of an
elbow formed upon the main shaft acting upon two arms, called wipers,
projecting from the rocking shaft, the angle formed by the arms exactly
coinciding with that of the elbow in its revolution. This admirable motion
will no doubt attract much attention from mechanists and engineers.

_The Lock Stitch from Two Reels_.--In the early days of the sewing machine,
the makers of it often met with the question, "Why do you use a shuttle at
all? Can you not invent a method of working from a reel direct?" The
questioner generally means a reel placed upon a pin, just as the upper reel
is placed. The reply to such a query is, of course, that to produce the
lock stitch in that way is impossible--as indeed it is.

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