All this being explained, it will be understood that the sole reason why the new power-houses at Niagara generate electricity is that electricity is the one readily transportable carrier of energy. We have already explained that there is loss of energy when the steam engine operates the dynamo. At Niagara, of course, no steam is involved; it is the energy of falling water that is transformed into the energy of the electrical current. Moreover, the revolving dynamo is attached to the same shaft with the turbine water-wheel, so that there is no loss through the interposition of gearing. Yet even so, the electric current that flows from the dynamo represents somewhat less of energy than the water current that flows into the turbine. This loss, however, is compensated a thousandfold by the fact that the energy of the electric current may now be distributed in obedience to man's will. "STEP UP" AND "STEP DOWN" TRANSFORMERS The dynamos in operation at Niagara do not differ in principle from those in the street-car power-house, except in the fact that they are not supplied with commutators. We have seen that these dynamos are of enormous size. Those already in operation generate five thousand horse-power; others in process of construction will develop ten thousand. The generator which produces this enormous current is about eleven feet in diameter, and it makes two hundred and fifty revolutions per minute. The armatures are so wound that the result is an alternating current of electricity of twenty-two hundred volts. This current represents, it has been said, raw material which is to be variously transformed as it is supplied to different uses. To factories near at hand, indeed, the current of twenty-two hundred volts is supplied unchanged; but for more distant consumption it is raised to ten thousand volts; and that portion which is sent away to the factories of Buffalo and other equally distant places is raised to twenty-two thousand volts. [Illustration: ELECTRICAL TRANSFORMERS. The upper figure shows Ferranti's experimental transformer built in 1888. It has a closed iron circuit, built up of thin strips filling the interior of the coil and having their ends bent over and overlapping outside. The lower figure shows a simple transformer known as Sturgeon's induction coil. The middle figure gives a view of the series of converters in the power house of the Manhattan Elevated Railway.]