18 
THE SEAWEEDS 
per cent, of iodine with 6.26 per cent, of potassium and 5.017 per cent, of 
sodium. At present the greater part of the world’s supply of iodine comes 
from the Caliche, the crude sodium nitrate of Peru and Chili, included 
in the form of sodium iodate. Again, these South American deposits 
cannot last for ever, and we may be obliged once more to rely on the 
concentrates of iodine made for us by the incessantly active algae. 
Other Uses.— The tougher kelps have been used in the manufacture of 
paper. In Japan, the potassium chloride of the kelps is used as the foun- 
dation in the manufacture of potassium chlorate for the making of matches. 
In Tasmania fishermen often moor their boats by tying them up to the 
stems of the “Bull kelp,” Sarcophycus, or of Macrocystis. In South 
Australia seaweed has been used as a foundation upon which to construct 
metal roads on loose sand, with apparent success, and algal limestones are 
used as road metal in the Coorong district. 
The Algae, being the simplest of self-supporting living organisms, 
present the problems of metabolism in the simplest known terms, and the- 
solution of these physiological problems may well be sought in the study 
of the Algae. 
