Straits. The waters are very tempestuous, and the navigation is made
more dangerous by the thousands of coral islands and coral reefs that
stud the ocean. Following the shoreline of Queensland, at a distance
of from ten to one hundred and fifty miles, and stretching for twelve
hundred and fifty miles, is the Great Barrier Reef of Australia, one
of the wonders of the world. The shelving floor of the ocean rises
nearly to the surface along this line, and vast colonies of coral
building creatures have formed their reefs up to the water's edge
along the ridge. The turbulent waves scouring over this living mass
have carved and moulded it into millions of fantastic islands,
sometimes heaping detached masses of dead debris high above the
surface of the water. At low tide the most wonderful fields of the
animal flowers of the sea are exposed. Some of them form branching
systems of hard skeletons like stony trees, the soft, brightly
coloured animals dotted over the stems like buds. Others form solid
masses; others, again, rounded skull like boulders, or elevations like
toadstools. The colours of the skeletons and the animals are vivid
scarlets and purples and greens. Sea anemones, shell-fish, and
starfish of the most vivid hues are as abundant as the corals.
Brilliant fish dart through the blossoms of the marine gardens, and
sea birds scream and wheel in the air. The whole region is a paradise
for the naturalist. Along the seaward side of the reef the great ocean
surges and thunders perpetually. Between it and the shore the quiet
channel glows under the tropical skies. It was amid such scenes as
these that the _Rattlesnake_ moved for nearly four years in the slow
work of taking soundings, fixing the exact position of channels
through the outer reef by slow triangular measurements, and generally
preparing for the safety of the commerce of all nations. The ship went
first up to Port Curtis in Brisbane; then fetched back to Sydney. Its
next trip was south to the strait between Tasmania and Australia,