of the cord. Naturally, the practical utility of these
discoveries was not overlooked by Galileo. Since a pendulum of a
given length oscillates with unvarying rapidity, here is an
obvious means of measuring time. Galileo, however, appears not to
have met with any great measure of success in putting this idea
into practice. It remained for the mechanical ingenuity of
Huyghens to construct a satisfactory pendulum clock.

As a theoretical result of the studies of rolling and oscillating
bodies, there was developed what is usually spoken of as the
third law of motion--namely, the law that a given force operates
upon a moving body with an effect proportionate to its effect
upon the same body when at rest. Or, as Whewell states the law:
"The dynamical effect of force is as the statical effect; that
is, the velocity which any force generates in a given time, when
it puts the body in motion, is proportional to the pressure which
this same force produces in a body at rest."[2] According to the
second law of motion, each one of the different forces, operating
at the same time upon a moving body, produces the same effect as
if it operated upon the body while at rest.


STEVINUS AND THE LAW OF EQUILIBRIUM

It appears, then, that the mechanical studies of Galileo, taken
as a whole, were nothing less than revolutionary. They
constituted the first great advance upon the dynamic studies of
Archimedes, and then led to the secure foundation for one of the
most important of modern sciences. We shall see that an important
company of students entered the field immediately after the time