Along comes a great wave, and perhaps they are torn up; but this does
not harm them, for they still live as they wash to and fro in the water,
until they cling to another rock. Or they are thrown on the shore to
die, or else to be washed back to sea by the next tide.

[Illustration: SEA-WEED FROND.]

The Sea Lettuce or Green Laver is a common seaweed near the shore. Its
broad, crinkled and bright green leaves are rather like those of a
lettuce. Sometimes it is boiled to a jelly and used for food. Many other
sea-weeds are good to eat, and on some coasts there is a regular
sea-weed harvest.

Now wade into rather deeper water, and you find a great mass of the
Bladder Wrack. Most schoolboys know it, for the little bladders of air
in the leaves explode with a pop if you squeeze them. The Bladder Wrack,
and others of the same kind, are torn up by the fierce waves in a storm,
and tossed on the beach in heaps. They are gathered by the farmer who
knows how to value a cheap manure for his fields. Some kinds are also of
use in packing lobsters so that they come to market nice and fresh.

When you have walked--in your diving dress--to deep water, you find
yourself among a tangle of olive-green weeds. They are below the line of
low tide. All round you is a forest of dark-green ribbons with wavy
edges. The ribbons are tough and very long, and cling tightly to the
rocks. These ribbon-weeds, and others of the same kind, are known as
Tangles. Round some parts of our coast they make wide, thick beds in the
sea. Though the ribbons may be six feet long, they are not so wide as
the palm of your hand.