Waterfalls

"The shaft into which the river hurls itself is an immense chasm, lined by glistening coal-black rock and narrowing into a creaming, boiling pit of incalculable depth, which brims over and shoots the stream over its jagged lip. The long sweep of green water roaring for ever down, and the thick flickering curtain of spray hissing for ever upward, turn a man giddy with their constant whirl and clamour."

Sir Arthur Conan Doyle, The Final Problem