Refrigerating...................    1/2 to 25

The motor power of a stream (Rose).

The power of a stream may be calculated by the following formula : P = Awh, in which A is the number of cubic feet of water falling in one second of time, w is the weight of a cubic foot of water, and h is the head or height through which the water falls. To reduce this to horsepower the formula should read : H.P. = Awhe/550, in which e represents the efficiency, in percentage, of the type of wheel to be used. The efficiencies of the various types of water-motors run about as follows : —

Per Cent

Turbines......................60-80

These values are only approximate, and may vary either way several per cent.

Hydraulic rams (Ogden).

The following table gives data as to size, capacity, and cost of hydraulic rams: —

 Size Flow ofSpring per Mm. Drive Discharge Water PumpedPER MlN. Cost of Ram gal. gal. No. 2...... 1 3/4 1/2 1/7 \$6.00 No. 4...... 5 l 1/4 1/2 1 8.00 No. 6...... 20 21/2 1 3 15.00 No. 10...... 50 4 2 7 35.00

This table is based on the assumption that the length of discharge pipe is not over 100 feet, and that the head against which the ram works is not over five times as great as the fall of the stream. The drive pipe should always be made as short as the conditions will permit. In winter the ram may be kept from freezing by housing it and providing a small coal fire for the coldest weather.

Hot-air engines (Ogden).

The following table gives data of sizes, capacities, fuel cost, of the hot-air engines commonly used : —

 Diameter of Cylinder Size of Pipe Fuel Consumption per Hour Capacity in Gal. Cost Gas cu. ft. Keros'e qt. Coal lb. inch 5........... 3/4 13 1/2 2 150 \$100 6 ............ 1 16 3/4 3 300 140 8.............. 11/4 20 l 4 500 175 10 ... . 11/2 50 2 5 1000 250