There are some underlying natural laws and other data relating to water
which every engineer should thoroughly understand. Heat, _water_,
steam, are the three properties with which he has first to deal.
_Weight of one cubic foot of Pure Water._
At 32° F. = 62.418 pounds.
At 39.1°F = 62.425 „
At 62° (Standard temperature) = 62.355 „
At 212° = 59.640 „
The weight of a cubic foot of water is about 1000 ounces (exactly 998.8
ounces), at the temperature of maximum density.
The weight of a cylindrical foot of water at 62° F. is 49 lbs.
(nearly). The weight of a cylindrical inch is 0.4533 oz.
There are four notable temperatures for water, namely,
32° F., or 0° C. = the freezing point under one atmosphere.
39.1° or 4° = the point of maximum density.
62° or 16°.66 = the standard temperature.
212° or 100° = the boiling point, under one atmosphere.
_Water rises to the same level in the opposite arms of a recurved
tube_, hence water will rise in pipes as high as its source.
_The pressure on any particle of water is proportioned to its depth
below the surface_, and as the side pressure is equal to the downward
pressure.
_Water at rest presses equally in all directions._ This is a most
remarkable property, the upward direction of the pressure of water is
equal to that pressing downwards, and the side pressure is also equal.
_Any quantity of water, however small, may be made to balance any
quantity, however great._ This is called the Hydrostatic Paradox, and
is sometimes exemplified by pouring liquids into casks through long
tubes inserted in the bung holes. As soon as the cask is full and
the water rises in the pipe to a certain height the cask bursts with
violence.
_Water is practically non-elastic._ A pressure has been applied of
30,000 pounds to the square inch and the contraction has been found to
be less than one-twelfth.
_The surface of water at rest is horizontal._ A familiar example of
this may be noted in the fact that the water in a battery of boilers
seeks a uniform level, no matter how much the cylinders may vary in
size.
_A given pressure or blow impressed on any portion of a mass of water
confined in a vessel is distributed equally through all parts of the
mass_; for example a plug forced inwards on a square inch of the
surface of water, is suddenly communicated to every square inch of the
vessel’s surface, however large, and to every inch of the surface of
any body immersed in it.