As the youths, with their glasses, eagerly scanned the coast they were approaching, one of them called out that he could see a strip
SPECIMEN OF CORAL.
of calm water close to the shore.
"We are coming to the great barrier-reef of coral," said Doctor Bronson, "and the calm water that you see is between the reef and the shore.
"Tahiti is one of the best examples of an island surrounded by a coral reef," the Doctor continued. "It extends quite around the island, sometimes only a few yards from it, and sometimes four or five miles distant. There are occasional openings through the reef, some wide and deep enough to permit the passage of large ships, and others practicable only for small boats. Inside the reef the water is calm, and a vessel once within it has a secure harbor."
The boys could see the surf breaking on the reef with great violence, and throwing spray high into the air. Outside was the ever-restless sea; inside lay the placid lagoon, which reflected the sunlight as in a mirror.
"Just think of it," said Frank; "that great reef, which resists the waves of the ocean, and could destroy the largest ship that floats, is built up by a tiny worm which we could crush between our fingers with the greatest ease. The patience of the honey-bee is nothing compared to that of the coral insect."
Fred asked what was the depth of water near the reef, both inside and outside.
