unt of modern machinery is of course directed not to
combining tools or series of productive processes upon which the
productive skill of man is closely engaged, but to substituting other
motors for the muscular power of man. But though certain tools as well
as certain forms of human effort are here replaced by machines, these
tools are not commonly embodied in the machinery for generating and
transmitting the new force, so that the mere consideration of the
different part played by the worker in generating productive force
does not assist us to distinguish a machine from a tool. A
type-writer, a piano, which receive their impulse from the human
muscles, must evidently be included among machines. It is indeed true
that these, like others of the same order, are exceptional machines,
not merely in that the motive power is derived more essentially from
human muscles, but in that the _raison d'etre_ of the mechanism has
been to provide scope for human skill and not to destroy it. But
though it is true that a high degree of skill may be imparted to the
first process of the working of a piano or type-writer, it is none the
less true that the "tool," the implement which strikes the sound or
makes the written mark, is not under immediate control of human touch.
The skill is confined to an early process, and the mechanism as a
whole must be classed under machinery. Nothing would indeed be gained
in logical distinctness if we were to abandon our earlier differentia
of the machine and confine that term to such mechanical appliances as
derived their power from non-human sources--the fact which commonly
marks off modern from earlier forms of machine production. For we
should find that this substitution of non-human for human power was
also a matter of degree, and that the most complex steam-driven
machinery of to-day cannot entirely dispense with some directing
impulse of human muscular activity, such as the shovelling of coal
into a furnace, though the tendency is ever to reduce the human effort
to a minimum in the attainment of a given output.

This consideration of the difficulties attending exact definitions of
machinery is not idle, for it leads to a clearer recognition of the
nicely graded evolution which has changed the character of modern
industry, not by a catastrophic substitution of radically different
methods, but by the continuous steady development of certain elements,
common to all sorts of industrial activity, and a