We now come to the use of water as power; and although in the last fifty years this subject has received little attention, as manufacturing increases and as fuel decreases and becomes higher, the value of water becomes more evident, and water-power sites are being eagerly sought. Our age may come to be known in the future as the age of power, because through the application of mechanical power man has gained such marvelous control over the world about him. Wind and water led in the production of power until about 1870, since which time they have scarcely increased at all, the greater advantages of steam and electricity having driven them out. As long as all factories had to be built by the side of streams having suitable water-power, the number and size of factories were always extremely limited. With the introduction of steam it became possible to build factories at mines, in forests, in fruit or grain regions, wherever the supply of raw material was plentiful, and to multiply factories of all kinds in cities near the markets for their product, or where labor was cheap and abundant. But power could only be used where it was developed, and the size of the power plant depended on the amount of business done by each individual user. Now a new era of power has again enlarged the possibilities of manufacturing. By means of electricity the work, not only of factories, but also of the home and the farm may be done in any place where electricity can be installed. We must bear in mind that electricity is never a source of power, but is only the agent that carries power to the user. The source of all electric power is either steam or water, produced by water-wheels, turbines, steam-engines or gas-engines. The economical way to furnish electric power is to establish central power plants, and electricity may be conveyed from them for many miles. An electric railway, telegraph, or telephone system many miles in length is operated from a single power plant. Electric light and power are transmitted all over the largest cities. It is no longer necessary that a factory be of any specified size nor that it have any waste power. If it be within reach of the electrical current it may use as much or as little as is needed. The cheapness of electric power must always depend on nearness to the source of supply or to the market. Until a short time ago it was customary to locate electric power-houses near the market, that is, in cities. But the benefits to be derived from having the electric plant near the source of power, so that the cost of production is greatly lessened, are becoming better recognized. This will make water-power increasingly valuable.