MANUFACTURE OF SALT FROM SEA-WATER 49 



this salt has been scraped into a pile and shoveled 

 into small boats, the bottom of the basins is then 

 rolled again, more sea-water is pumped in, and the 

 salt making continued. The ponds are connected to 

 the main salt yards by means of small canals through 

 which the salt barges can be propelled. 



The European Solar Process 



In France, Spain, Portugal, Italy, and other 

 countries bordering on the Mediterranean, sea-salt 

 has been prepared by the solar process for several 

 centuries. The methods used in these countries are 

 also in use in many other parts of the world, e. g., 

 the West Indies, South America, and Africa. A mod- 

 ification of the process has been used in California 

 for many years. 



Since sea-water contains only about three per cent 

 of salt, thirty-two tons of water must be evaporated 

 for each ton of salt produced. The use of coal or 

 other fuel to effect the evaporation of this enormous 

 amount of water would make the cost of the salt 

 produced almost prohibitive. For this reason the 

 manufacture of salt from sea-water can compete 

 successfully with the mining of rock-salt and the 

 production from salt wells only when that industry 

 is located in warm dry countries where solar evapo- 

 ration of the water is practicable. Moreover the 

 salt works must be constructed on level land adjoin- 

 ing a bay or the ocean. The ground underlying the 

 site of the salt works must be nearly impervious to 

 water. Clays and clayey marls are most satisfactory. 



The amount of salt which can be produced on a 



