I think that I had better light a blue light." Frank nodded.

The blue light at once blazed out.
"They ought to see that if they are not all asleep," Frank said, as he looked up at the sails standing out white against the dark sky.
"Set to work with that foghorn," the skipper said; and a man began to work the bellows of a great foghorn, which uttered a roar that might have been heard on a still night many miles away.

Again and again the roar broke out.
"That has fetched them," the captain said.

"She is starboarding her helm to go astern of us.

There, we have lost her red light, so it is all right.