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ted salts, if given in large quantities, are poisonous, one 400tb part 

 of its own weight ol marine salt will kill any animal. Sea water 

 owes its bitter taste to the sulphate of magnesia it contains, better 

 known to most of you as Epsom Salts. Pliny tells us the ancient 

 Eomans used to transport waters of the Dead Sea at enormous 

 cost into Italy, where its curative properties were highly prized. As 

 we know, the waters of the Dead Sea contain relatively more saline 

 matter, than any other sea, no less indeed, than six times as much. 

 We all know how much easier it is to swim in sea water than in fresh, 

 but so great is the density of the water of the Dead Sea that it is 

 difficult to sink in it, and the body of a man floats on its surface. 

 This great density is due to the fact that no considerable rivers flovr 

 into the Dead Sea, so that the loss by eva-poration goes on more 

 rapidly than the supply of fresh water. This is the reason why 

 tropical oceans are more salt than northern seas. At the tropics 

 evaporation goes on so rapidly that tliree-quarters of an inch of the 

 surface water is taken up in twenty-four hours, which amounts to 

 a layer of no less than 22 feet each year, while in the north, 

 evaporation is far less rapid, and the sea receives enormous 

 volumes of ice, which is practically fresh water. Sea water ice, 

 when dissolved, contains no saline matter, or rather it contains 

 only a very small proportion which is mechanically entangled 

 amongst its particles. Gea water, when pure, is quite inodorous ; 

 when it has any smell, it is because it contains animal or vegetable 

 matter in solution or suspension, as often happens on our coasts or 

 in harbours.' Oysters and other shell fish, especially mussels, will 

 live and thrive in sea water loaded with animal matter in a state of 

 decomposition ; part of this they absorb and transform in their 

 interiors into certain very poisonous alkaloids, which chemists call 

 Ptomaines. This is the explanation of the poisonous effects 

 occasionally produced by eating muscles and other shell fish. Al- 

 though sea water is, owing to the salts of magnesia it contains, 

 usually very unpleasant to the taste, yet oyster eaters will recall 

 the agreeable taste of the water found in the shell of the oyster, 

 and which the animal has stored up in order to carry on respiration. 

 This is due to the fact that this pent up fluid contains always more 

 or less of the vital juices of the animal itself, which was wounded 

 by the knife in the act of opening the shell. 



The problem how to render sea water drinkable, has engaged 

 the attention of mankind for at least 1800 years, and even now, 

 despite all our science and chemical improvements, remains prac- 

 tically unsolved. Pliny asserted that a bottle hermetically sealed 

 and sunk deep into the sea, would return to the surface filled with 

 pure water. This statement was implicitly believed until modem 

 times, when a sceptical Italian (Cosigny) tried the experiment, 



