MUR

MUR

C 124 )

be carried on in the, lieight of fummer, thecords can be charged no more than twice or atthe utrnoft thrice in the year.

The ialt is broken by a kind of moveableflail fet in a frame in which each row of cordsis placed in turn.

The country of Saltzbourg on the borders ofthe Tyrol furnifhes a vaft fupply of fait, whichis procured from a large fait mountain near thetown of Hallein . No brine fprings are foundhere, which is a remarkable circumftance, as ingeneral the neighbourhood of rock fait aboundsin water. The rock fait however is not work-ed out in mafs in this country, but an artificialbrine is made in the following manner. f Ahorizontal gallery is cut in the mountain throughthe middle of the rock fait, from 50 to 200fathoms in length, 5 feet high, and 4 wide.This gallery is fupported above and on thefides by planking, and the opening is {hut upby an earthen wall. Frefh water is then let infrom fprings collected on the upper part of themountain, till the whole gallery is filled. Intwo or three weeks the water by refting on thefait has acquired 22 per cent, of faltneis, after■which it is drawn off and boiled down as ufual.This procefs is then repeated as often as ne-ceflary, till by degrees the galleries by thegradual folution of the fides and floor enlargeinto vaft caverns. The roof never enlarges,which is rather a Angular circumftance.

The fea is an inexhauftible fource of fait, andvaft quantities of it are made from fea-waterin different countries. Sea-water is but a weakbrine, the folid contents of which vary in diffe-rent parts of the world. In the Baltic it is notmore than in the Britifh Channel aboutand taken at a great depth near the Equator, itis about -5Vi in which ftate its fpecific gravity is1.0289, according to Bergman, who has ana-lvfed it. By the experiments of this excellentchemift it appears that an Englifh wine pint ofthis fea-water (of 28.875 cubic inches) contained

grains.

Of Muriated foda - 241

— Muriated magnefia 65.5— Sulphat of lime - 8.

3 *4-5

A fmall portion of carbonated magnefia alfofeparates during the evaporation.

Sea-water therefore contains a very largeproportion of other faline matters befides com-mon fait, more fo than the common brine fprings,

and this being chiefly muriated magnefia, thefait procured from fea-water is apt to be bitterand l'ubject to deliquefcence unlefs a good dealof pains be taken in the boiling, cr unlefs theevaporation be conducted very flowly. Thereare feveral ways of getting the lalt by iea-water :in warm climates this is done altogether by theheat of the atmofphere, and this forms the large-grained ftrong dry fait called bay fait, which ijpreferred to any other for curing provifions thatare intended to keep for a length of time. Bavfait is made in great perfection in Spain andPortugal , by the Bifcayans, and on the Medi-terranean ftiores of France , and in the Bahama,iflands in the Weft Indies. The procefs is Ampleand requires but little apparatus of any kind.The firft requifite is a fea marfh, or {hallowartificial pond, near enough to the fea to befilled at high water. A level fliore mult there-fore be chofen, and the foil muft be clayey toretain the water. The bottom of the pond isthen laid out perfectly even, and beaten hardand fmooth, and a channel with flood-gates iscut to the fea. The fait pools confift alwaysof a large refervoir communicating directly withthe fea at one end, and at the other with a num-ber of fmaller pits or beds on which the fait ismade. The water is firft evaporated by thefun’s heat confiderably in the refervoir, and thenconveyed to the falt-beds, which are only a fewinches deep, and in which the evaporation iscompleated alfo by the fun and wind, and thefait feparates firft in the form of a white cruftwhich is broken from time to time to expofe afrelh furface to the air. The concentrated brineyields fait about twice and fometimes thrice 2week in fummer. The firft faline cruft thatforms is fmal 1-grained, the latter large. Bayfait has generally a little tinge of colour, greenor brown, according to the foil on which it isformed. It is only made in the fummer months.

Another way of making fait from fea-water,and which is praftifed much on the French andother coafts of temperate climates, is partly bythe atmofpherical evaporation and partly byboiling, for the fummers are not hot enough inthis climate to make fait by mere expofure ofbrine to the air. The general mode of proceedingis that already mentioned, that is to fay, thefea-water is expofed during the fummer in {hal-low artificial pools, where it becomes highlyconcentrated, and this is afterwards boiled downin iron pans in the ulual mode. This way isadopted largely in Scotland , and in a few partsof England, particularly at Lymington . The

Joural des Mines, No. 76.