"In the first place," said Lord Hastings, "they are so small that they escape the notice of a submarine until the motorboat is almost upon them; and then it is too late for them to act. Also, the motorboat, being small, is a much more difficult object to hit with a torpedo—it is, in fact, a very poor target. Then again, a motorboat is so much swifter than a submarine that the advantage is all with the motorboat."
"By Jove, sir! the way you explain it I can see the advantages," said Jack eagerly.
"And so can I," agreed Frank.
Lord Hastings smiled.
"You are easily convinced," he replied. "Had some of the admiralty officials been convinced half so easily, this submarine menace might have been effectually stopped long before this."
As the motorboat continued down the Thames, each occupant remained busy with his thoughts. It was Frank who broke the silence.
"What has happened to the torpedoboat destroyers, sir?" he asked. "I understood they were the real submarine foe, with their heavy nets."
"They are still in use," replied Lord Hastings. "You know how they work their nets, I suppose?"
"Why, I think so, sir. The net is carried by two ships, and when a submarine crashes into the net she either tangles her nose or her stern in the net and can be disposed of with ease."
"Yes, but what I want to know," said Jack, "is why she doesn't fire a torpedo through the net and sink the torpedoboat?"