7 j GEOLOGY. 



from Barcelona, and seven from the central ridge of the Pyrenean chain. The formation 

 in this locality includes the hill on which the town is situated, and the environs to a con- 

 siderable extent, which are diversified by various eminences composed of the mineral, 

 but one in particular, called the mountain of red salt, from that colour predominating, is 

 most prominent, from its insular character, its great mass, its sharp forms, and the red 

 and white hues, the vivacity of which contrasts with the grey and sallow tints of some 

 surrounding rocks. It has been well described by M. Cordier, in the Annales des Mines 

 for 1817, and by Count A. Laborde, in his Travels in Spain, " The colours," , says the 

 latter, " vary with the altitude of the sun, and the greater or less quantity of rain. At 

 the foot of the mountain a spring of water issues, which comes through a fissure we per- 

 ceive on the summit. The rivulet runs all along the valley from the east, but passes 

 under ground in part of its course, particularly under the hill where the rock-salt is 

 mined ; it rises again to the surface at a little distance, and, after running along the plains, 

 discharges itself into the river Cardona. This brook in rainy seasons swells the waters 

 of the river, which then become salt, and destroy the fish ; but at three leagues lower, the 

 water has no perceptible taste of salt. All the salt mountains are intersected by crevices 

 and chasms, and have also spacious grottoes, where are found stalactites of salt, shaped 

 like bunches of grapes, and of various colours; nothing can compare with the magnifi- 

 cence of the spectacle which the mountain of Cardona exhibits at sunrise. Besides the 

 beautiful forms which it presents, it appears to rise above the river like a mountain of 

 precious gems, displaying the various colours produced by the refraction of the solar rays 

 through a prism." 



Saliferous strata occur upon an immense scale in Hungary and Poland, and in Western 

 Asia, referable to various geological eras ; but the extensive beds of rock-salt and gypsum 

 near Bex in Switzerland, so long considered as a decided example of such rocks occur- 

 ring in the more ancient deposits, have been shown by Dr. Buckland to belong to the 

 new red sandstone formation. The chief site of the mineral in England is in the marl 

 of Cheshire, where, with a few exceptions, it is f<pund in the valleys of the Weaver and 

 its tributary streams, in some places manifesting its presence by springs impregnated 

 with salt ; in others, being known by mines carried down through the substance of the 

 strata. At Northwich the brine springs are very abundant, formed by the penetration 

 of spring or rain waters to the upper surface of the rock-salt, in passing over which they 

 acquire a degree of strength, modified by various circumstances, in some instances 

 approaching to the point of perfect saturation of the brine. Here, also, many mines have 

 been sunk for the purpose of working out the fossil salt, which was first discovered in the 

 year 1670 in searching for coal. It forms two great strata or beds, lying nearly horizontal, 

 but on different levels, the superincumbent being separated from the subjacent stratum by 

 several layers of indurated clay or argillaceous stone, irregularly penetrated by veins of 

 salt. The upper stratum is found from 28 to 48 yards below the surface of the earth, 

 the superior soil consisting of white clay and gypsum, the latter appearing in connection 

 with the salt of Hungary, Poland, and Transylvania. This bed, varying in thickness 

 from twenty to thirty yards, has a reddish-brown colour, not much unlike sugar-candy, 

 and consists of muriate of soda, mixed with a small portion of oxide of iron, which gives 

 it its tint. The lower stratum, which has never been entirely perforated, is remarkably 

 different from the upper in appearance, consisting of almost pure muriate of soda, generally 

 perfectly white and clear as crystal. It is only in this purer bed that mining operations 

 are now carried on, about 60,000 tons being annually taken from the pits at Northwich, 

 besides not less than 45,000 tons being manufactured from the brine springs. 



The formation of rock-salt and gypsum is in general referred to deposition from the 

 waters of the sea. Dr. Holland, from the appearance of the plain constituting the salt 



