WIELIEZKA SALT MINES 21 SLANICU, RUMANIA, INTERIOR OF SALT MINE 25 WIELIEZKA SALT MINES 29 SUBSIDENCE OF LAND, NORTHWICH 41 DUNKIRK SUBSIDENCE, NORTHWICH 49 THE CANAL-BURST AND LANDSLIP NEAR NORTHWICH IN 1907 59 A SALT STORE-SHED 67 WITTON BROOK, SUBMERGENCE OF AGRICULTURAL LAND 75 WORKING IN DANGEROUS GROUND AFTER SUBSIDENCE, DUNKIRK LAKE, NORTHWICH 81 STREET-RAISING IN PROGRESS--HIGH STREET, NORTHWICH 89 THIS ROAD WAS RAISED TWENTY FEET IN TWENTY YEARS. NONE OF THESE BUILDINGS IS NOW STANDING--NORTHWICH 93 INTERIOR PENNY’S LANE MINE, NORTHWICH 99 REMARKABLE SUBSIDENCE IN NORTHWICH 111 A ROW OF OPEN PANS 119 ILLUSTRATION OF FOUR SCOTT PATENT DOUBLE EFFECT SALT EVAPORATORS, WITH AUTOMATIC SALT DISCHARGERS, SALT CONVEYORS, AND HYDRO-EXTRACTORS 131 THE HODGKINSON PATENT SALT-MAKING PLANT 137 SALT AND THE SALT INDUSTRY CHAPTER I THE CHEMISTRY AND PROPERTIES OF SALT “Salt” was the name which was given in the first place to the residue left by the evaporation of sea-water, but the designation was subsequently employed to include the other substances held in solution in the sea, and, at a still later period, the name was still further extended by chemists to cover all the combinations of a base and an acid which are now classed as “salts.” Sodium, or sodic chloride Na Cl, which is now distinguished as “common salt,” is an example of the simplest type of chemical salt, its molecule consisting of one atom of the metal sodium combined with one atom of the gas chlorine, both sodium and chlorine being mono-valent elements, _i.e._, one atom of each being able to unite with, or displace from a compound, one atom of hydrogen.