There are other methods of utilizing the fall of a stream, but usually they involve a greater outlay for the construction of a dam and other appurtenances. An old-fashioned bucket water wheel may be used, which, though not efficient, utilizes the power of the stream. The wheel may be belted or geared to a pump directly or may drive a dynamo, the power of which may in turn be transmitted to the pump. The objection to such construction usually is that during the summer the small streams which could be made of service at slight expense run dry or nearly so, while the expense of damming and utilizing a large stream where the water-supply is always sufficient is too great for a single house. _Hot-air engines._ The simplest kind of a pump worked mechanically is the Rider-Ericsson hot-air engine (see Fig. 46), which is made to go by the expansive force of hot air. The fuel used may be wood, coal, kerosene oil, gasolene, or gas, the amount used being very moderate and the daily expense of maintenance very small. [Illustration: FIG. 46.--A hot-air engine.] For a number of years the writer used one of these machines to pump water from a tank in his cellar to a tank in the attic, so that running water could be had throughout the house. With an engine and pump costing $100, it was necessary to pump twice a week for about an hour to supply the attic tank and to furnish the necessary water for the family. The following table shows the dimensions, the capacity, and the fuel consumption of the different styles of pumps made by this company:-- TABLE XII =========+===========+===========+=========+==========+============+====== | Suction | | | | | | and | | | | Anthracite | Size of | Discharge | Capacity | Cu. Ft. | Kerosene | Coal Per | Cylinder | Pipe | Per Hour | of Gas | Per Hour | Hour | Price ---------+-----------+-----------+---------+----------+------------+------ 5" | 3/4" | 150 gal. | 12 | 1 qt. | 4 lb. | $ 90 6" | 1" | 300 gal. | 16 | 2 qt. | 4 lb. | 130 8" | 1-1/4" | 500 gal. | 20 | 2 qt. | 5 lb. | 160 10" | 1-1/2" | 1000 gal. | 50 | 3 qt. | 6 lb. | 240 =========+===========+===========+=========+==========+============+====== _Gas engines for pumping._