60 THE WEALTH OF THE SEA 



weed-burning industry is a curious survivor from 

 the days when large factories were unknown. In 

 those days farmers and fishermen were manufac- 

 turers of chemicals. The farmers prepared potash 

 for use in the making of soap, glass, and alum by 

 leaching hardwood ashes, and the fishermen made 

 potash similarly by leaching the ashes of seaweed. 

 Even as late as the beginning of the nineteenth cen- 

 tury, seaweed burning was one of the most impor- 

 tant industries of Scotland, and twenty thousand 

 tons of kelp ashes valued at four hundred thousand 

 pounds sterling were produced annually. When the 

 manufacture of soda from common salt commenced, 

 the value of the seaweed ashes dropped rapidly, and 

 the production declined until 1841, when large 

 amounts of iodine began to be produced from this 

 source. The demand and the price for iodine in- 

 creased until 1873, when the supply was greatly 

 increased by the recovery of this element from the 

 mother liquors left after the extraction of sodium 

 nitrate from caliche, which is found in the arid 

 regions of Chile. 



To-day the seaweed-burning industry is located 

 principally in Scotland, Normandy, Norway, and 

 Japan; small amounts of seaweed are also burned in 

 Sweden, Denmark, and Norway. Since about 400,- 

 000 long tons of green seaweed are annually col- 

 lected in Europe, each ton yielding about a pound 

 of iodine, the entire European production of iodine 

 is approximately 400,000 pounds. Japan produces 

 an equal amount. 



