obliquely to the direction in which they move. This kind of fly or vane
is generally used in the smaller kinds of mechanism, and, unlike the
heavy fly, it is a destroyer instead of a preserver of force. It is the
regulator used in musical boxes, and in almost all mechanical toys.

_Increase and Diminution of Velocity._--Twisting the fibres of wool by
the fingers would be a most tedious operation; in the common
spinning-wheel the velocity of the foot is moderate; but, by a very
simple contrivance, that of the thread is most rapid. A piece of cat-gut
passing round a large wheel, and then round a small spindle, effects
this change. The small balls of sewing cotton, so cheap and so
beautifully wound, are formed by a machine on the same principle, and
but a few steps more complicated. The common smoke-jack is an instrument
in which the velocity communicated is too great for the purpose
required, and it is transmitted through wheels which reduce it to a more
moderate rate.

_Extending the Time of Action in Forces._--The half-minute which we
daily devote to the winding up of our watches is an exertion of labour
almost insensible; yet, by the aid of a few wheels its effect is spread
over the whole twenty-four hours. Another familiar illustration may be
noticed in our domestic furniture: the common jack by which our meat is
roasted, is a contrivance to enable the cook in a few minutes to exert a
force which the machine retails out during the succeeding hour in
turning the loaded spit.

_Saving Time in natural Operations._--The process of tanning formerly
occupied from six months to two years; this time being apparently
required in order to allow the tanning matter to penetrate into the
interior of a thick hide. The improved process consists in placing the