more extensive project — the Isles des Chaussey Project which in- 

 volves building a dam across the bay of Mont St. Michel. The 

 output of this scheme would supply a half of France's present 

 electricity consumption. 



From time to time there has been talk of reclaiming land from 

 the sea, on a scale far greater than that achieved by the Dutch. In 

 1928 the German engineer Herrmann Sorgel proposed his Atlan- 

 tropa Project, without doubt the greatest engineering venture ever 

 contemplated by man. His idea was to alter the geography of much 

 of the continent of Africa. Setting aside all political and technical 

 implications, the basis of the plan lay in building dams across the 

 Strait of Gibraltar and the Dardanelles, isolating the Mediterranean. 



At present the water exchange through the Strait of Gibraltar 

 results in a net inflow of water from the Atlantic into the Medi- 

 terranean. Together with inflowing water from rain and other 

 sources, there is a total annual inflow of about three and a half 

 million, million tons of water, but all of it is lost by the intense 

 evaporation over the Mediterranean. By building two dams the 

 inflow would be cut down by about sixty-five per cent and the level 

 of the Mediterranean would fall. Sorgel calculated that the level 

 would drop about five feet a year, but more recent estimates suggest 

 a rate only half as much, so it would take more than a hundred 

 years for the level to drop the 330 feet he envisaged, thereby ex- 

 posing new land for cultivation. In addition, vast amounts of 

 power would be generated at aU the river mouths. 



At present, while surface water of the Atlantic flows into the 

 Mediterranean, the very salty, and consequently heavier, water of 

 the Mediterranean flows at deep levels into the Atlantic, joining 

 the great deep currents of that ocean. These deep currents are impor- 

 tant to man in many ways. For one, they are a tempting repository 

 for radioactive wastes that are accumulating at an alarming rate 

 from atomic energy plants. At the moment, however, we know 

 very little about the speed of these deep currents, and in particular 

 the rate of vertical exchange of water, so we are unable to say just 

 how quickly waste deposited at the bottom of the sea might rise to 

 the surface and polute our fish. 



The deep currents contain great quantities of the nutritive salts 

 needed by plant plankton, but these currents do not mix easily with 

 the shallower waters where the plankton thrive. If we could bring 

 this rich, deeper water to the surface in certain areas we would 

 enrich the surface layers with a ready-made fertilizer for the plant 

 plankton. The temperature and salinity structure of some parts of 

 the ocean are of such a nature that we might use them to achieve 

 this end. 



In many parts of the tropical and subtropical oceans the salinity 

 of the warm surface waters is higher than that of the deeper, colder 

 waters. If, therefore, a long thin-walled tube were lowered into the 

 deep water, and then by means of a pump the deep waters were 

 started flowing up the tube, they would continue flowing up 

 even after the pump were taken away. The reason for this is 

 simple. As the deep water flowed slowly up the tube it would be 

 warmed by conduction of heat through the thin wall of the tube, 

 and so at the same level inside and outside the tube the water would 

 be at the same temperature. Because the water inside the tube is less 

 salty — and therefore less dense — than the outside water, the water 



Sea 

 level 



V 



Warm lesi salme 

 waler reaches 

 the surface 



Warm, more 

 saline water 



less 

 watei 



>aline 

 gradual!" 



attains the 

 temperature 

 of the water 

 outside the 

 icibe 



valine water 



This theoretical scheme shows one way of 

 bringing nutrient-rich deep water up to 

 the surface to provide a fertilizer for 

 the plant plankton. Once started by a 

 pump, the deep water rising up the tube 

 would continue flowing up to the surface 

 forever, even after the pump were taken 

 away (for explanation, see text). 



242 



