aler spills over 

 mto reservoir 



pre^iling direct tin of 

 movament of watar 



In an attempt to harness the energy of waves 

 a V-shaped concrete structure was set up 

 on the Algerian coast. Waves are funneled 

 Into the open end of the V, the water then 

 spilling over the narrow end Into a 

 reservoir. The steady outflow of water 

 from the reservoir operates a turbine from 

 which power can be generated. 



Britain, the United States, and the Middle East, for instance — this 

 process has already been done for us by nature. Extensive deposits 

 of rock salt — the remains of seas of a distant geological age — have 

 been laid down by nature, and it is more economical to mine them 

 directly than it is to process sea water. In some countries, on the 

 other hand, where there are no rock salt deposits, imported salt is 

 expensive, so the production of salt by evaporation becomes anj 

 attractive proposition. 



A more recently exploited chemical product of the sea is mag- 

 nesium, the demand for which has increased rapidly ever since theJ 

 aircraft industry has required lighter and stronger alloys. Because] 

 the sea has large supplies of magnesium — about four million tons 

 in a cubic mile of water — processes have been devised by which it I 

 can be extracted at a competitive cost. 



Although the sea contains a great store of elements, its future asl 

 a source of supply must depend on demand, and on the competitive 

 cost of extracting them from the land. At present potassium, for I 

 example, is obtained mainly from salt deposits or from the Dead! 

 Sea, which has an unusually high potassium content compared with 

 sea water. In spite of this, the prospect of extracting potassium 

 directly from the sea appears promising as a result of the develop- 

 ment of a new extraction process. 



Men have long been tempted by the possibility of extracting] 

 gold and silver from the sea. After the First World War, Germany ] 

 sponsored an expedition — the Meteor Expedition — to attempt to 

 extract enough gold to pay the German war debt, but the concen- 

 tration of gold found was less than a tenth of the expected amount. 

 At present it would cost more to extract the gold and silver from I 

 the sea than these metals are worth. In time, however, as man | 

 exhausts the land supply of certain chemicals, he may be forced to j 

 turn to the sea as his major supplier. 



While the sea is a vast storehouse of food and minerals, it is also ' 

 a gigantic source of energy. Even in these days of atomic energy, j 

 engineers are considering means of producing power from the sea. 

 One method that has been proposed is the generation of power j 

 from the thermal energy of the sea. It is based on the principle that l 

 the change of heat into energy requires a hot source and a cold j 

 source. In driving a steam engine, for example, we boil water (hot j 

 source) to make steam which passes through the cylinders then is 

 cooled in the condensers (cold source). In tropical and subtropical I 

 latitudes there is a substantial difference in temperature between 

 the surface water and deep water. Because water boils at progres- 

 sively lower temperatures as the atmospheric pressure is reduced, 

 it would be possible to boil the warm surface water by piping it 

 into low pressure containers, then introduce the steam into a 

 turbine. For a cold source, to convert the steam back into water, 

 the cold, deep water which Ues close to the shore could be used. 

 To pump this cold water to the surface would require little energy, \ 

 for the effective height it would have to be raised is merely that ' 

 from the sea surface to the power station. French scientists have 

 tried to assess the practical possibilities of such a scheme, and after j 

 pilot trials plans have been drawn up for a full scale generating! 

 station at Abijan on the Ivory Coast. 



The most obvious source of power would seem to be the endless 

 train of waves that wash against the shore. There is a wide spectrum j 



240 



