A HARVEST FROM THE OCEAN. m 



fifty pounds to one ton of the wet weed), so complete was the em- 

 bargo against Spanish barilla and salt that kelp assumed a value 

 as high as one hundred dollars per ton. During this halcyon 

 period Scotland and her western isles reaped an annual income of 

 nearly three million dollars, a sum which raised to affluence many 

 a Scottish lord whose sole possession hitherto had been a long 

 title and a few miles of barren sea-shore. But the end of the war, 

 and the success of Le Blanc's process for making sodium car- 

 bonate out of common salt, brought down the value of kelp with 

 a sudden and disastrous drop. In 1831 the price had fallen to ten 

 dollars per ton, a figure no longer remunerative. At this period 

 kelp-making would have died out entirely but for the presence in 

 it of a small quantity of iodine. The discovery of that element in 

 1812, by Courtois, and the demands for its manufacture, which had 

 arisen between that date and 1840, were the sole cause for the 

 continuance of kelp-making ; for kelp was then, and has since 

 remained, the only practicable source of iodine in Europe. Dur- 

 ing the past fifty years kelp has furnished fully ninety per cent 

 of all the iodine and iodides which commerce has handled. The 

 remaining ten per cent comes from South America, being derived 

 from the well-known caliche of Peru. This substance, in being 

 worked for the large amount of nitrate of soda it contains, also 

 gives a small quantity of iodine as a profitable by-product. The 

 caliche yields from two to three pounds of iodine per ton, against 

 an average yield of twelve or fifteen pounds on the part of kelp. 

 Many bothering questions of manipulation increase the labor and 

 cost of the product from the former source, thus leaving the com- 

 mercial advantage with kelp. With the origin of this new demand 

 for kelp the industry received a strong impulse, and the price was 

 restored to fairly profitable figures, ranging from fifteen to twenty 

 dollars per ton, at which price it is still in commerce. 



It may be proper to note several interesting facts connected 

 with the growth and composition of iodine-bearing weeds. All 

 sea-weeds do not contain iodine, although that substance is uni- 

 versally present in sea- water in the ratio of one to two hundred 

 and. fifty thousand, proportions which, though minute, are amply 

 sufficient to tempt assimilation by all growing sea-plants at least 

 to an appreciable extent. Yet very few of them outside the family 

 of Algai. contain even a trace of that element. So that to this 

 family has been committed the chief work of withdrawing iodine 

 from sea- water, and of concentrating it in plant-tissues in a form 

 easy of extraction. The power of iodine absorption on the part of 

 the Algol is the more remarkable when it is remembered that their 

 growth transpires in the presence of three hundred times as much 

 of the very similar element bromine, which latter, however, is ab- 

 sorbed in only one tenth the quantity. The localities where they 



