376 ^^6 Philippine Journal of Science 1915 



that it came to be worth twelve pesos ' for half a fanega [i (55.501 liters) ], 

 although its ordinary price was two or three reals [25 to 37.5 centavos] — 

 and some years even less, depending on the (height of the) water and on 

 the heat of the sun, on which conditions this so necessary industry depends. 



These and other letters tell of the production of salt at an early- 

 date in many parts of the Islands. During the following years 

 mention is made by many writers of the barter of salt and other 

 articles of food on the one hand, and gold on the other, between 

 those who lived along the coast and the inhabitants of the 

 mountains. 



All processes for salt making fall into three groups, depending 

 on the character of the heat employed and the manner of its 

 application: (1) Use of solar heat, or solar salt manufacture; 

 (2) direct artificial heat, or kettle and pan processes; (3) steam 

 heat, or grainer methods.* The majority of the plants in the 

 Philippine Islands belong to the first group; there are a few 

 in the second, and none in the last group. 



USE OF SOLAR HEAT IN DIFFERENT PROCESSES 



In warm climates, as upon the shores of the Mediterranean, 

 the coast of California and Mexico, the entire Pacific coast of 

 South America, the islands of the West Indies, Southern Aus- 

 tralia, and the whole coast line of tropical Asia, including China 

 and Japan, sodium chloride is obtained by the evaporation of 

 sea water in the shallow lagoons or in shallow basins or pools, 

 constructed upon the seashore and exposed to the sun's rays. 



France is one of the most important sea-salt-producing 

 countries of Europe. The total area covered by the salt works 

 is about 19,000 hectares, in 12 departments — 7 on the Mediter- 

 ranean and 5 on the Atlantic coast. In this industry some 8,000 

 laborers are employed for several months every year.^ 



Portugal, Spain, and Italy are also among the chief sea-salt- 

 producing countries of Europe. 



Italy is the cradle of the saltern industry. Pliny relates that 

 Ancus Martius, the fourth of the early kings of Rome, who 

 reigned from 640 to 616 before Christ, was the first who had 

 sea water led into closed basins to evaporate for salt. Later 

 many such salterns were established, so that even in very early 

 times the manufacture of sea salt was an important industry. 

 An interesting relic of this is the Via Salaria — the salt road — one 



' One peso Philippine currency equals 100 centavos, equals 50 cents 

 United States currency. 



*nh Annual Kept. U. S. Geol. Survey (1886), 505. 



'Furer, Salzbergbau (1900), 269; Bull. La. Geol. S^irv. (1907), 7, 158. 



