along channels for irrigation and domestic
purposes, using dams and sluice gates to control
the flow. The ancient Cretans had an elaborate
plumbing system. Archimedes studied the laws of
floating and submerged bodies. The Romans
constructed aqueducts to carry water to their
cities.
After the breakup of the ancient world, there
were few new developments for many centuries.
Then, over a comparatively short period,
beginning near the end of the seventeenth century,
Italian physicist, Evangelista Torricelle, French
physicist, Edme Mariotte, and later, Daniel
Bernoulli conducted experiments to study the
elements of force in the discharge of water
through small openings in the sides of tanks and
through short pipes. During the same period,
Blaise Pascal, a French scientist, discovered the
fundamental law for the science of hydraulics.
Pascal’s law states that increase in pressure on
the surface of a confined fluid is transmitted
undiminished throughout the confining vessel or
system (fig. 1-1). (This is the basic principle of
hydraulics and is covered in detail in chapter 2
of this manual.)
For Pascal’s law to be made effective for
practical applications, it was necessary to have a
piston that “fit exactly.” It was not until the latter
part of the eighteenth century that methods were
found to make these snugly fitted parts required
in hydraulic systems. This was accomplished by
the invention of machines that were used to cut
and shape the necessary closely fitted parts and,
particularly, by the development of gaskets and
packings. Since that time, components such as
valves, pumps, actuating cylinders, and motors
have been developed and refined to make
hydraulics one of the leading methods of trans-
mitting power.
Figure 1-1.—Force transmitted through fluid.
Use of Hydraulics
The hydraulic press, invented by Englishman
John Brahmah, was one of the first work-
able pieces of machinery developed that used
hydraulics in its operation. It consisted of a
plunger pump piped to a large cylinder and a ram.
This press found wide use in England because it
provided a more effective and economical means
of applying large forces in industrial uses.
Today, hydraulic power is used to operate
many different tools and mechanisms. In a
garage, a mechanic raises the end of an auto-
mobile with a hydraulic jack. Dentists and barbers
use hydraulic power, through a few strokes of a
control lever, to lift and position their chairs to
a convenient working height. Hydraulic doorstops
keep heavy doors from slamming. Hydraulic
brakes have been standard equipment on auto-
mobiles since the 1930s. Most automobiles are
equipped with automatic transmissions that are
hydraulically operated. Power steering is another
application of hydraulic power. Construction
workers depend upon hydraulic power for the
operation of various components of their
equipment. For example, the blade of a bulldozer
is normally operated by hydraulic power.
During the period preceding World War II,
the Navy began to apply hydraulics to naval
mechanisms extensively. Since then, naval
applications have increased to the point where
many ingenious hydraulic devices are used in the
solution of problems of gunnery, aeronautics, and
navigation. Aboard ship, hydraulic power is used
to operate such equipment as anchor windlasses,
cranes, steering gear, remote control devices, and
power drives for elevating and training guns and
rocket launchers. Elevators on aircraft carriers use
hydraulic power to transfer aircraft from the
hangar deck to the flight deck and vice versa.
Hydraulics and pneumatics (chapter 11) are
combined for some applications. This combina-
tion is referred to as hydropneumatics. A n
example of this combination is the lift used in
garages and service stations. Air pressure is
applied to the surface of hydraulic fluid in a
reservoir. The air pressure forces the hydraulic
fluid to raise the lift.
STATES OF MATTER
The material that makes up the universe is
known as matter. Matter is defined as any
substance that occupies space and has weight.
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