220

MODERN STEAM PRACTICE.

upper end of the pipe, with a trough having a flap valve in thebottom for passing the water direct into the cistern if required.

By means of an indicator diagram we can calculate the amountof work required to raise the water from the lower tank to the highreservoir as follows:—The measuring box is 6 feet X 3 feet 3 inches x3 feet 1 inch, and has a capacity of 60-64 cubic feet. The aver-ages of four experiments made by the engineer for the works gave5 8'2 5 seconds as the time required to fäll the box, which representsa discharge of 62-5 cubic feet per minute. The area of the plungerof the pump being '9398 foot, and the double stroke 6 feet—theengine making thirty-five revolutions per minute, which represents11 - 66 of the plunger—gives a theoretical discharge of 6573 cubicfeet per minute, and shows a ratio between the theoretical andactual of 100 : 95, or a loss of 5 per cent. This represents an amountof work = Ö2'5 cubic feet, weighing 3906 lbs., raised 202 feet high,which is equal to an expenditure of 23.9 horse-power. The indi-cator diagram showed an effective pressure of 23 lbs. per squareinch, which with thirty-five strokes per minute at 6 feet, with a pistonof 2247 square inches, is = 33 horse-power, showing a loss for fric-tion, &c., of 27 per cent.

CONSUMPTION AND COST WITH VARIOUS KINDS OF COAL.

per ton. per hour. per horse-power per horse-power

* * per hour, per hour.

Broomhill Nuts at6/6 ... burn 37 cwts. ... = 17'3 lbs. ... = -602 d.

Berwick Hill.. 9/6 ... ,, 2-5 ,, ... = 117 ,, ... = ' 586 ( 7 .

Scremerston.,, 9/6 ... ,, 27 ,, ... = I2'6 „ ... = ■631a'.

The above table compares the consumption and cost of coal withthe actual quantity of water delivered, which is equal to an expen-diture of 24 horse-power. If we compare the expense of workingthis engine with larger ones in use at some of the English waterworks, and use the same Standard—namely, the cost of raising 1000gallons 100 feet, which is equal to 1,000,000 foot-pounds, we find—

The Trent Water-works Company at Nottingham.cost *287^.

Boulton & Watts, 29 horse-power, 1809, condensing,. ,, *543^.

3 °'Ä „ „ ,, . „ - 358 ^

»» >> 76 „ 1828, „ .. -333(7.

Berwick Pumping Engine, 1871 (high-pressure),.. ,, *340^.