"Not if it wasn't for the warships," agreed Frank. "And there are enough of them to make it hot for any hostile fleet. But it's a wonder to me some of these German submarines haven't taken a little trip up the Thames."
"Mines," replied Jack briefly.
"True," said Frank, "but you will remember we took a pretty long jaunt up the Dardanelles, and passed through the Kiel canal."
"And when you stop to think of it, we're pretty lucky to be here right now," returned Jack dryly.
"Well, so we are, if that's the way you look at it. However, I wouldn't mind having another such chance."
"You'll probably get it."
Conversation lagged as the boys took in the scenes about them; and there was little more talk during the trip. They stopped more than once, and, loitering along, it was dark when they neared their destination.
As they would have drawn up to the wharf there was a sudden flash of light—gone in a moment—followed by a dark body that swished by them like a flash.
Frank uttered an exclamation of astonishment.
"See that?" he demanded.