10. Of tools. The difference between a tool and a machine is
not capable of very precise distinction; nor is it necessary, in
a popular explanation of those terms, to limit very strictly
their acceptation. A tool is usually more simple than a machine;
it is generally used with the hand, whilst a machine is
frequently moved by animal or steam power. The simpler machines
are often merely one or more tools placed in a frame, and acted
on by a moving power. In pointing out the advantages of tools, we
shall commence with some of the simplest.
11. To arrange twenty thousand needles thrown promiscuously
into a box, mixed and entangled in every possible direction, in
such a form that they shall be all parallel to each other, would,
at first sight, appear a most tedious occupation; in fact, if
each needle were to be separated individually, many hours must be
consumed in the process. Yet this is an operation which must be
performed many times in the manufacture of needles; and it is
accomplished in a few minutes by a very simple tool; nothing more
being requisite than a small flat tray of sheet iron, slightly
concave at the bottom.
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