“Swallows,” said Bevis; “I can see some swallows, high up, there. That’s another sign of land.”
“Heave the lead,” said Mark.
“We’ve forgotten it; how stupid! Mind you remember it next time.”
New Formosa was a long way in the rear now.
“That’s Pearl Island,” said Mark, pointing to a larger sandbank. “Can’t you see the shells glistening; it’s mother-of-pearl.”
“So it is.”
The crows had carried the mussels up on the islet, and left the shells strewn about. The inner part reflected the sunlight. If examined closely there are prismatic colours.
“There’s that curious wave,” said Mark, standing up and pointing to an undulation of the water on the other side of a small patch of green weeds. The undulation went away from them till they lost sight of it. “What is it?”
“There are all sorts of curious things in the tropic seas,” said Bevis. “Some of them are not found out even yet. Nobody can tell what it is.”
“Perhaps it’s magic,” said Mark.