The next important epoch was the invention of Forneyron in 1823, of the water-wheel known as the Turbine and also as the Vortex Wheel. If we will return a moment to the little steam engine of the ancient Hero of Alexandria, called the Eolipile, it will be remembered that the steam admitted into a pivoted vessel and out of it through little opposite pipes, having bent exits turned in contrary directions, caused the vessel to rotate by reason of the reaction of the steam against the pipes. In what is called Barker’s mill, brought out in the 18th century, substantially the same form of engine is seen with water substituted for the steam. A turbine is a wheel usually placed horizontally to the water. The wheel is provided with curved internal buckets against which the water is led by outer curved passages, the guides and the buckets both curved in such manner that the water shall enter the wheel as nearly as possible without shock, and leave it with the least possible velocity, thereby utilising the greatest possible amount of energy. In the chapter on Electrical inventions reference is made to the mighty power of Niagara used to actuate a great number of electrical and other machines of vast power. This utilisation had long been the dream of engineers. Sir William Siemens had said that the power of all the coal raised in the world would barely represent the power of Niagara. The dream has been realised, and the turbine is the apparatus through which the power of the harnessed giant is transmitted. A canal is dug from the river a mile above the falls. It conducts water to a power house near the falls. At the power house the canal is furnished with a gate, and with cribs to keep back the obstructions, such as sticks. At the gate is placed a vertical iron tube called a penstock, 7½ feet in diameter and 160 feet deep. At the bottom of the penstock is placed a turbine wheel fixed on a shaft, and to which shaft is connected an electric generator or other power machine. On opening the gate a mass of water 7½ feet in diameter falls upon the turbine wheel 160 feet below. The water rushing through the wheel turns it and its shaft many hundred revolutions a minute. All the machinery is of enormous power and dimensions. One electric generator there is 11 feet 7 inches in diameter and spins around at the rate of 250 revolutions a minute. Means are provided by which the speed of each wheel is regulated automatically. Each turbine in a penstock represents the power of 5,000 horses, and there are now ten or more employed. After the water has done its work on the wheels it falls into a tunnel and is carried back to the river below the falls. Not only are the manufactures of various kinds of a large town at the falls thus supplied with power, but electric power is transmitted to distant towns and cities.