"I say, mister, 'ow is it done ?" he went on.
"It is a simple thing when you know the secret," said De Sylva.

"Have you passed Fernando Noronha before, Captain ?" "Many a time." "Have you seen the curious natural canal which you sailors call the Hole in the Wall ?" "Yes, it's near the s'uth'ard end." "Well, the sea has worn away a layer of soft rock that existed there.
In the course of centuries a channel has been cut right across the two hundred yards of land.

Owing to the same cause the summer rains have excavated a ravine through the crater up above, and a similar passage exists here, only it happens to run parallel to the line of the cliff.
It extends a good deal beyond its apparent outlet, and is defended by a dangerous reef.

Marcel once landed on a rock during a very calm day, and saw the opening.

He investigated it, luckily for me--luckily, in fact, for all of us." Watts interrupted De Sylva's smooth periods by a startled ejaculation, and Coke turned on him fiercely.
"Wot's up now ?" he demanded.