When water in a vessel is subjected to the action of fire it readily imbibes the heat, or fluid principle of which the fire is the immediate cause, and sooner or latter, according to the intensity of the heat, attains a temperature of 212p Fahrenheit. If, at this point of temperature, the water be not enclosed, but exposed to atmospheric pressure, ebullition will take place, and steam or vapor will ascend through the water, carrying with it the superabundant heat, or that which the water cannot, under such circumstances of pressure, absorb, to be retained, and to indicate a higher temper-ture.

Water, in attaining the aeriform state, is thus uniformly confined to the same laws, under every degree of pressure; but, as the pressure is augmented, so is the indicated temperature proportionately elevated. Hence the various densities of steam, and corresponding degrees of elastic force.

Practical Properties Of Water

By analysis it is ascertained, that water is composed of the gases oxygen and hydrogen in a state of chemical union; its distinguishing properties, like that of other liquids, being nearly incompressible gravity, capability of flowing, and constant tendency to press outwards in every direction; also that of being easily changed by the absorption of caloric to an aeriform state of any required density or degree of clastic force: hence the principle of the hydraulic press, the water-wheel, the steam engine, etc.

Effects produced by Water in its Natural State

Because of liquids possessing the properties of gravity and capability of flowing freely in every direction, sides of vessels, flood gates, sluices, etc., sustain a pressure equal to the product of the area multiplied by half the depth of the fluid, and by its gravity in equal terms of unity.

But when a sluice or opening through which a liquid may issue is under any given continued head, the pressure is equal the product of the area multiplied into the height from the centre of the opening to the surface of the fluid.

Example 1. - Required the pressure of water on the sides of a cistern 18 feet in length, 13 in width and 9 in depth.

The terms of measurement or unity are in feet; 1 cubic foot of water = 62-5 lbs.; hence,

18 X 9 X 2 + 13 X 9 X 2 - 558 X 4-5 X 62.5 = 156987.6 lbs. weight of water on bottom = 18X 13X9 X 62.5 - 131625 lbs.

Example 2. - Required the pressure on a sluice 8 feet square, and its centre 30 feet from the surface of the water

3 X 3 X 30 X 62.5 = 16875 lbs. pressure.