ROCK SALT, 

 of the most diathermanous of known sub- 

 stances. H. 2. S.G. 2-03 to 2-15. 



Fig. 366. 



Conip. Chloride of sodium ; orNaCb 

 sodium 39-6, chlorine 60-4= iOO. 



Analysis, from Cheshire, by Henry : 



Chloride of sodium . .98-32 

 Sulphate of lime . . . 0'65 

 Chloride of magnesium 



Chloride of calcium 

 Insoluble matter . 



0-02 

 0-01 

 1-00 



100-00 



Fuses at a red heat, and forms a crystal- 

 line mass on cooling. Volatilizes at a white 

 heat. 



This mineral is the source of the common 

 salt of commerce. 



Salt is one of the principal articles of 

 commerce mentioned in Domesday, and 

 brought a considerable revenue to the 

 crown before the Norman conquest. Half 

 a million tons of salt are annually produced 

 in this country at the present day, chiefly in 

 the Valley of the Weaver in Cheshire, from 

 immense beds belonging to the New Hed 

 Sandstone. One-fifth only of the above 

 quantity is raised in the form of Rock Salt, 

 the remaining four-fifths being obtained 

 from brine-springs. 



The principal salt-works in England are 

 at Northwich, Wins'brd, IMiddlewich and 

 Nantwich in Cheshire; at Droitwich in 

 Gloucestershire ; at Shirleywich in Stafford- 

 shire ; in Durham ; and at Carrickfergus, 

 near Belfast. Formerly considerable quan- 

 tities of salt were obtained by the evapora- 

 tion of sea-water in salterns or shallow pits, 

 on the coast of Hampshire and the Isle of 

 Wight, as it is now practised on the shores 

 oftlie Mediterranean, &c. ; but this source of 

 supply has very much diminished of late 

 years. 



There are immense deposits of Rock Salt 

 in Spain, in Old and Xew Castile, and also 

 at Cardona, in Catalonia, where it forms se- 

 veral hills, one of which is said to be between 

 400 and 500 feet high. It also forms hills in 

 ]\Ioldavia. The other principal localities are 

 Dieuze and A'ic, in France ; Bex, in Switzer- 

 land; Wieliczka,.in Poland; Hungary; 

 Transylvania; Ischel, Berchtesgaden and 



ROCK SALT. 321 



Hallein, in the North Eastern Alps, where 

 the fibrous blue variety, which occasionailv 

 occurs at Hall in the Tyrol, is also some"^- 

 times found. Djebel Melah and Ouled Keb- 

 bah, in Algeria, and verj' extensively dis- 

 tributed in the north of Africa, on both 

 sides of the Atlas Mountains. • Southern 

 Russia, bet^'een the rivers Ural and Vole-a. 

 At Ileksaia-Zachtchita, in the steppes'^of 

 the Kirghiz, the Rock- Salt is crystalline, 

 white without a stain, and so pure that 

 the salt is at once pounded for use without 

 undergoing any cleansing or recrystalli- 

 zation. 



Large quantities of Rock Salt occur near 

 Lake Oroomiah, in the N.W. of Persia. In 

 the Desert of Caramania, according to 

 Chardin, it is so abundant, and the atmo- 

 sphere so dry, that houses are built of it. 

 The salt of Lahore in the Punjab forms a 

 hill as large as that of Cardona, and is cut 

 into dishes, plates, and stands for lamps. 

 Other localities are Cashmere, Abyssinia, 

 China, Peru, the Cordilleras of New Gra- 

 nada, the United States (chiefly in Silurian 

 sandstones in the middle and western 

 st^ates), forming brine springs at Salina in 

 New York, in the Kenawha Yalley (Vir- 

 ginia), Muskingum in Ohio, and in Ken- 

 tucky ; also forming beds with Gypsum in 

 Virginia, Washington co., and in the Salmon 

 River Mountains of Oregon. California. 

 The salt found at the bottoms and sides of 

 salt-lakes is the lake-salt of Jameson (.S'ee- 

 salz of Reuss and Werner). It is collected 

 in the islands of Cyprus and Milo, in the 

 Mediterranean; in the neighbourhood of the 

 Caspian, in the Crimea ; and might be ob- 

 tained, at a small cost, from many of the 

 shallow lakes situated about 40 miles W. of 

 Geelong, in Victoria. There are, also, salinas 

 or natural salt-lakes on the eastern side of 

 S. America, in the argillaceo-calcareous 

 deposits of the Pampas ; in the sandstone of 

 the Rio Negro, about fifteen miles above the 

 town of El Carmen ; and in the pumiceous 

 and other beds of the Patagonian tertiary 

 formation, often several leagues in diameter, 

 and generally very shallow. Victoria ; in the 

 Desert, towards the junction of the rivers 

 Darling and Murrunibidgee with the river 

 Murray. 



Great quantities of fine white salt ai-e 

 afforded by two salt-lakes at Manzelack, 

 near Alexandria ; by salt-lakes in Caffraria ; 

 and from the lake of Dombu, in the great 

 desert of Bilma in Bornu. 



Salt is in all countries one of the neces- 

 saries of life, and is employed for a variety 

 of purposes— chiefly as a seasoning for food, 



Y 



