PROPERTIES AND CONSTITUTION OF SEA -WATER. 533 



will not give it up again. Sucli substances are lime, chalk, potash, 

 soda, and calcined bones, all common and cheap. 



The problem of freshening sea-water was formerly regarded as so 

 important that other means of solving it besides that of evaporation 

 were advanced. Even the great Leibnitz lent his name to a proposi- 

 tion which was judged singular, if nothing worse, by his contempora- 

 ries. It was to freshen water by forcing it through a filter filled with 

 litharge ; but he never tried the experiment. It was believed, on the 

 authority of Pliny, that if an empty bottle, hermetically sealed, were 

 sent down deep into the ocean, it would come back full of pure water. 

 But it was proved that the bottles would either be broken or come back 

 empty. Other naturalists tried filters of earth or sand. But, when 

 Reaumur and the Abbe Nollet constructed a gigantic filter of glass 

 tubes filled with sand, a thousand toises long, they found that the 

 water came out of it as salt as it went in. Lister, in 1684, placed sea- 

 weeds with their stems in water, after the fashion of a bunch of 

 flowers, in an alembic which he did not heat, believing that the fresh 

 water would ooze out in drops from the upper part of the plants ; but 

 he had to acknowledge that no gi'eat result came from his curious pro- 

 cess. Samuel Reyer made a discovery of some practical value — that 

 melted sea-ice furnished a potable water. Notwithstanding numerous 

 distilling apparatus were devised by various inventors, ships con- 

 tinued to be furnished until very recently with water stored in casks. 

 The inventions had little practical value, and the management of 

 alembics when the sea was rough was a matter of considerable dif- 

 ficulty. 



The sea is in reality an immense and inexhaustible mineral spring. 

 Probably, if it only contained pure water, a fountain as rich in mineral 

 matters as the ocean actually is would attract crowds of drinkers and 

 would be recommended for internal use in all imaginable diseases. 

 But sea-water is abundant and common, and has never been much used 

 internally. On the other hand, the therapeutic employment of sea- 

 baths might be made the occasion of long dissertations. 



It is generally known that a strong dose of sea-water acts as an 

 emetic ; in weaker proportions it is purgative and diuretic. Dios- 

 corides advised diluting it with honey, which might, perhaps, produce 

 an efiicacious medicine, but certainly not a savory one. At the be- 

 ginning of this century it was diluted with wine, but such a mixture 

 could hardly be better than the other one. It was prescribed in Spain 

 against the yellow fever, and in England against worms : in the for- 

 mer case, as an emetic ; in the second case, milk was added to it so 

 that the child could drink it without aversion. Sea-baths have been 

 tried as remedies for hydrophobia and insanity, but, it is needless to 

 say, without efl'ect. 



Marine water contains a little iodine ; it is therefore a resolvent, and 

 adapted to external application for tumors and ulcers, although more 



