360
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THE SEAS
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it provides a clear gelatinous medium upon which cultures
of bacteria may be-grown.
Seaweeds contain certain chemical bodies the extraction
of which can be carried out on a commercial basis.
In
Scotland the wrack that is swept up on the beach by the
waves is collected and burnt in kilns and iodine, bromine
and potash are obtained.
Great care must be taken to
collect these weeds before they are rained upon as the fresh
water quickly washes out the iodine.
For this reason
the harvesting and subsequent treatment of these weeds
,
is & summer industry.
Iod'me and potash are also obtained
from seaweed in other parts of the world and the industry
_
was much encouraged in America during the great war.
A further substance, alginic acid,'can also be extracted
”from these weeds, and the substance hardens to form a
_
good inSulating material.
There are also many derivatives
‘
of the acid which can be used for making size and for other—
purposes.
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