If tidal power is to be utilized at all it must be done on a grand scale. A French engineer, R. Esnault Pelterie, has proposed a vast tidal power system in the English channel where the tide rises high. (See map Fig. 55.) The plan is a most ambitious one, but the power that could be obtained is enormous. He proposes to build concrete dikes across the channel at the Straits of Calais inclosing a large basin about twenty miles wide and turbines would be operated by the flow of water into and out of this basin. Of course locks would have to be provided to permit the passage of ships through the basin. Other and larger basins could be formed by walling off the estuary of the Thames and the bay of the Seine on the French coast. The Gulf of St. Malo could be inclosed by running a dike from Cape La Hague to the island of Guernsey and thence to the mouth of the Trieux. These basins would furnish a minimum of 800 horsepower for each square mile, hence the basin across the Straits of Calais alone would furnish nearly half a million horsepower while the Gulf of St. Malo would furnish about a quarter of the power that France now uses in her industries. The first cost of the installation would be heavy, but there would be no expense for fuel and the supply of power would be endless. It has been proposed to dam the estuary of the Severn (England) where the spring tides rise thirty feet, and it has been estimated that half a million horsepower would be developed. Part of the power would be used to pump water into an elevated reservoir which would serve as a storage battery, so that when the tidal plant was idle because of the turn of the tide, water flowing out of the reservoir would operate an auxiliary plant, thereby furnishing a continuous supply of power. POWER FROM SUNSHINE With the exception of the tides all the energy we use on earth comes from the sun. It is the sun’s energy that is stored in coal beds and oil fields; it is the sun’s energy that raises water from the ocean to the tops of our mountains; it is the sun’s energy that makes the winds blow, and through them disturbs the surface of the ocean, and even the tides owe a part of their energy to the attraction of the sun. Why can we not utilize the energy of the sun directly, instead of at second hand? In the sunshine that beats upon the earth there is seventy-thousand times as much energy as we now obtain from coal. Unfortunately the energy of the sun is so widely dispersed that it cannot be used economically except in a very few places where clouds do not often interrupt the direct passage of the rays to the earth’s surface.