Page:Popular Science Monthly Volume 26.djvu/549

Rh will not give it up again. Such 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 proposition which was judged singular, if nothing worse, by his contemporaries. 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 Réaumur and the Abbé 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 seaweeds 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 great result came from his curious process. 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 continued 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 difficulty.

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. Dioscorides advised diluting it with honey, which might, perhaps, produce an efficacious medicine, but certainly not a savory one. At the beginning 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 former 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 effect.

Marine water contains a little iodine; it is therefore a resolvent, and adapted to external application for tumors and ulcers, although more