8. The Celtiberian or Spanish District.—This is rather a number of isolated mines and brine springs. The chief towns aro Saelicas, in the province of Guadalajara ; Torreximeno, in the province of Jean ; Villafafila, in the province of Zamora ; Monteagudo and Minglanilla, in the province of Cuenca ; Cazorla and Hinojares, in Andalusia ; and Jmnilla, iu the province of Clhinchilla. There arc indications of salt in various other places ; indeed, Spain seems richly endowed with this mineral.
9. Iaolated Salt-Deposits and Brine-Springs.—In France, at the foot of the Alps, at Moutiers and Casteliana, are well-known brine-springs from which salt is made. These may possibly belong to the same district as those of Aigle and Bcx. In Italy, at Volterra in Tuscany, salt is manufactured ; and at Lungs° and Altamonte, in the mountains of Calabria, rock-salt is mined. In Sicily, at Nicosia and Mussomeli, are salt deposits. At Szamobor, in Croatia, and Tuzla, in Bosnia, salt ie found. In Russia, at Bachmutz, on the Donetz ; Balachna, on the Volg,a ; Staraia Russo, near Lake Ilmcn ; Solikamsk, on the Kama, and the neighbourhood of the Ural Mountains; and at Iletzkaya, salt deposits exist ; also at Eupatoria, in the Crimea, rock.salt is found. In Prussia, at Jnowraclaw, Rawicz, Waltersdorf, brine-springs are found ; and at Sperenberg, S. of Berlin, a bed of rock-salt, of the enormous thickness of 2810 ft., bad been bored into in 1870. At Kreuznaoh, on the Nahe, rock-salt is mined : this seems to be connected with the Vosges.
10. Cheshire, Worcestershire, &a—The chief centres of rock-salt and brine-springs are North Middlewich, Winsford, Sandbaeh, in Cheshire ; Weston-on-Trent, in Staffordshire; Stoke Prior, and Droitwich, in Worcestershire. At Dunerue, near Carrickfergus, there is an important rock-salt deposit. At Middlesborough-on-Tees, another valuable deposit of rock-salt exists. At Chester-le-Street, in Durham, is a brine-spring. Indications of salt are to be met with in Stafford shire, Shropshire, and Lincolnshire. The Cheshire and Worcestershire deposits are by far the most important among British rock-salt deposits, the Carrickfergus salt being only worked t,o a comparatively limit,ed extent, and the Middlesborough hitherto not at all. This last was discovered some years ago by Bolckow, Vaughan, it Co., while boring for water in their steel-works, but they were unable to follow up the discovery fer want of sufficient room. Bell Bros. have now bored in the meadows in front of their works at Port Clarence, where, at a depth of a little over 300 yd., they have again found the salt, and have traversed the bed to a thickness of about 33 yd. No doubt with cheap coal and the facilities for ehipment existing at the spot, as well as its proximity to the important industrial centres of the Tyne, the Wear, and the Tees, and its central position on the E. coast of England, the produce of this deposit may some day find its way t,o the Baltic, and supply part of the Scotch and English fisheries, and figure as an important factor in tho salt industry of England.
Rock-salt, as such, is comparatively little worked in England at the present day, only about 115,000 tons being annually sent down the river Weaver, and most of this coining from the celebrated Marston mine, owned by Fletcher and Rigby of Northwioh. This is the most extensive rock-salt miue in Glreat Britain. The rock-salt is mostly exported to Belgium, and some other Continental countries. Germany used to take some rock-salt from England, but since her own discoveries, this trade has greatly diminished. Some consumption of ground rock-salt has sprung up of late, for use in the Hargreaves process of making " salt-cake " (see p. 287), for which it is better suited than the ordinary chemical salt. The rock-salt was first discovered at Marbury in 1670, in trying for coal, and for about a century subsequently only the upper layer of salt was known and worked. As far as the deposits in tho neighbourhood of Northwich are known, each is said to consist of two superimposed beds, and to form two separate blocks, about miles long and 1300 yd. wide, but they are obviously far larger than this. The salt is reached at depths varying from 32 to 53 yd. (at Marston, 37 yd.), by sinking through beds of variegated clays or marls interstratified with layers and nodules of gypsum. The upper bed of rock-salt possesses a thickness of 25-30 yd., but rapidly thins off towards the S.-W. Above this bed of salt, and lying apparently in the recesses of its surface, is found a more or less continuous layer of saturated brine. This is the brine which, extracted at the various pumping-stations of Northwich,Winsford, and other places, and evaporated as described later on, supplies the white salt of the works of these districts. It bas obviously been produced by leakages or infiltrations of the surface water through fissures in the superincumbent strata, and this by prolonged contact with the rock-salt has become converted into brine. Once
saturated witli salt, this brine lies inert upon the rock-salt, producing no further solvent action, until, seine of it being withdrawn by pumping, more fresh water flows in from above, or until water, entering the strata at any outcrop which may exist on higher grounds, forces the brine out to the surface as natural springs, and continues the solution of the rock-salt. It is estimated that the quantity of brine pumped in the Cheabire salt districts must in this way annually withdraw not leas than 1,122,900 cub. yd. of rock-salt from the subjacent strata, leaving the ground above practically unsupporttd. In many places, serious damage to property has arisen from this cause, and, in a bill lately attempted to be iutroduced before Parliament, it Nvas proposed to compensate the losses and destruction of property consequent upon these subsidences by a tax of 3d. a ton to be levied on all the salt manufactured in the Cheshire districts ; but the bill was rejected. A very exhaustive inquiry was made by a select Committee of the House of Commons on this occasion, which lasted frum May 5th to May 20th of the preaent year, into the geological relations of the Cheshire sali ferous strata. Several interesting points wore mised ss to the causes of the subsidences, and De Rance, of the Geological Survey, among others, afforded some valuable historical and practical scientific evidence, the general conclusions at which he arrived being :-1. That the brine is formed by the natural descent of water through the porous strata of the bigh grounds surrounding the geological basin of Cheshire on to the saline beds. 2. That the brine so formed passes by gravita tion through the strata, emerging from it in several places at the surfaee of the ground. 3. That this wastage of the sidiferous beds has, previously to the interference of man, caused large subsidences in historic times, and is likely still to continue to do so. The evidence adduced with regard to the existence of natural brine-springs and the records of previous subsidences were very interesting, and it seems difficult to imagine how now, after some centuries of working, and in view of the above facts, a tax such as that proposed could be levied on the saltmakers without injustice. One very curious map was placed in the hands of the committee, showing how very large have been the workings in the Northwich region, and that, practically speaking, nearly the whole district is undermined by the excavations for rock-salt, most of these being in the upper bed, and this was held sufficient to acc,ount for much of the subsidence in that region. In France, similar ac,cidents have occurred, only to a less extent, from similar causes; and part of the fortifications of the town of Dieuze having been injured by subsidence in the celebrated salt-mines of that place, the waters of the Indre having penetrated into the mines and dissolved the supporting columns of salt, the French Government felt bound to legislate on the matter. The mine of Varengeville, St. Nicolas, also fell in a few years since, causing some loss of life, and considerable destruction of property. Beneath the upper bed of the rock-salt at Northwich, lies one of a kind of greystone, interstratified with veins of salt. This bed of saliferous stone is 101 yd. thick, and overlies the second or great bed of salt, below which it reappears, and has been sunk into to a further depth of about 62 yd. in another mine adjoining the Marston, where some small layers of salt were found, but of infe,rior quality. The second bed is the one from whieh the principal supplies of British rock-salt are now drawn ; and at Marston, it has been explored to about 33 yd. in thickness. The Marston mine has been worked for over 100 years, is 120 yd. in depth, and covers an arca of about 40 acres. Round the base of the shaft, the roof of the mine is supported by eight huge pillars of rock-salt, each pillar being 30 yd. long by 10 yd. wide. The rest of the mine is equally supported by pillars, between which the salt has been worked out ; these are 10 yd. sq., and 25 yd. apart. The main or principal cutting in the mine is called by the miners Piccadilly. The salt is blasted out with gunpowder in the ordinary fashion, and sent up in bens to the surface ; the best and purest portions are selected for sale, while those which are too much contaminated with clay are rejected. This description of a rock-salt mine might be repeated for nearly every other salt mine in the world, with the sole difference that in some (as in Wieliczka) the workings are on a more vast and important scale.