A gallon of water (U. S. standard) weighs 81/3 pounds and contains 231 cubic inches. A cubic foot of water weighs 621/2 pounds, and contains 1,728 cubic inches or 71/2 gallons.

Doubling the diameter of a pipe increases its capacity four times. Friction of liquids in pipes increases as the square of the velocity.

The mean pressure of the atmosphere is usually estimated at 14.7 pounds per square inch, so that with a perfect vacuum it will sustain a column of mercury 20.9 inches or a column of water 33.9 feet high.

To find the pressure in pounds per square inch of a column of water, multiply the height of the column in feet by .434. ' Approximately we say that every foot elevation is equal to 1/2 pound pressure per square inch; this allows for ordinary friction.

To find the diameter of a pump cylinder to move a given quantity of water per minute (hundred feet of piston being the standard of speed), divide the number of gallons by four, then extract the square root, and the product will be the diameter in inches of the pump cylinder.

To find the quantity of water elevated in one minute running at one hundred feet of piston speed per minute: Square the diameter of the water cylinder in inches and multiply by four. Example: Capacity of a five-inch cylinder is desired. The square of the diameter (five inches) is twenty-five, which, multiplied by four, gives one hundred, the number of gallons per minute (approximately).

To find the horse power necessary to elevate water to a given height, multiply the total weight of the water in pounds by the height in feet and divide the product by 33,000 (an allowance of twenty-five per cent should be added for water friction, and a further allowance of twenty-five per cent for loss in steam cylinder).

The area of the steam piston, multiplied by the steam pressure, gives the total amount of pressure that can be exerted. The area of the water piston multiplied by the pressure of water per square inch gives the resistance. A margin must be made between the power and the resistance to move the pistons at the required speed - say from twenty to forty per cent, according to speed and other conditions.

To find the capacity of a cylinder in gallons. Multiplying the area in inches, by the length of stroke in inches, will give the total number of cubic inches; divide this amount by 231 (which is the cubical contents of a U. S. gallon in inches), and the product is the capacity in gallons.