Sea-Water, denotes the saltwater of the ocean.

The salts which this fluid contains, are, 1. Common marine, or culinary salt, compounded of fossil alkali, or Soda, and marine acid ; 2. Salited magnesia, or a saline substance formed by the combination of marine acid with magne-sian earth; 3. A small portion of selenite, or gypsum. - The quantity of saline matter obtained from the water of the British seas, is estimated by NeumaNk, to be about one ounce in each pint. - See also the article Salt, p. 14.

Sea-water is of great utility for various purposes. It affords an excellent manure, either sprinkled on land, by means of the machine described in the article Kitchen-GaRden ; or, when it is mixed with putrescible matters, formed into a compost, and distributed over the soil. In a medicinal view, Dr. Russel (Dissertation concerning the Use of Sea-water in Diseases of the Glands, etc. 8vo.) states the following cases, in which this fluid may be drunk with advantage, namely, in all glandular obstructions, as well as in swellings of the neck, and other parts ; in all cutaneous diseases ; in recent obstructions of the liver and kidnies (provided the stone in the latter be not large) ; in bronchocele, or tumors in the wind-pipe ; and, lastly, for the prevention of the bilious colics, to which mariners are frequently subject.

As many persons, afflicted with the complaints before, mentioned, have not an opportunity" of resorting to the sea-side, for the benefit of the water, different ex have been devised, to preserve this fluid from putrefaction. For such purpose, Mr. HeNRy made a Variety of experiments, which are related in the first vol. of the "Me-vudrs of the Literary and Philosophical Society of Manchester :" - the results of these, however, exceeding our limits, we shall merely observe that, from his first attempt, two scruples of quick-lime appear to be sufficient for preserving one quart of sea-water.

To purify the sea-water from its saline ingredients, so as to render it fresh, is an object of the greatest importance to navigators ; for various accidents may happen, by which the stock of this necessary article on ship-board may be spilt, or become corrupted. - In the year 1734, Mr. Appleby discovered a process, which for a short time was adopted in the Navy. It consisted in distilling sea-water with a certain quantity of lapis infernalis (which has since been discovered by Dr. Butler to be simply the rough salt of tartar), and calcined bones, or rather quick-lime ; but such method was soon disused, on account of the difficulty with which it was attended, and the disagreeable taste it imparted to the water. Dr. B. therefore proposed, as a substitute for Mr. ApplEby's ingredients, the distillation of sea-water with soap leys, in the proportion of one quart of the latter to 15 of the former ; which he asserts (in his Safe, Easy, and Expeditious Method of procuring any Quantity of Fresh Water at Sea, etc. 8ov.1755, will produce 12 gallons of fresh water but the objections before stated have also been applied to this pro-cess. - Dr. Halls recommended pulverized chalk ; which, however, is said to be too expensive, and does not improve the taste of the le fluid. Sea water may be easily div ed of its salt taste, by distilling it With wood-ashes, particularly with those obtained from the beech-tree. The same desirable object may be effectted, by filtring the fluid through sea-weed; and we conceive, that other marine vegetables might be employed with equal advantage. But the most simple apparatus is that invented by Dr. Irving, for which he received a reward of 50001. By this contrivance, all stills, still-beads, etc. are rendered unnecessary ; because the common boiler or kettle belonging to a ship, will serve as an effectual substitute : with this ought to be connected, a plain tube made of plate-iron or sheet-tin, that may be easily procured on board. As soon as the sea-water is poured into such vessel, the tube must be fitted to the lid or cover, round which a piece of wet linen may be applied, to adapt it the better to the mouth of the new still. When the water boils, the vapour should be suffered to pass freely for a minute, in order to clear the tube, which is then to be constantly moistened, by passing a mop dipped in the sea along its upper surface. The distillation should be continued till three-fourths of the water be drawn off, when the brine ought to be taken out : thus, any quantity of pure water may be obtained, without the aid of any ingredients. The utility of this expedient is obvious ; and we trust that it is, or at least Will be, generally adopted on board of every ship that is bound to a distant port.