"Now let her rip," cried the other, for in climbing to get the required height to rush the Channel, the machine had lost speed.
"Right-o!" came the answer.
So, in order to get speed quickly, Dastral did a little nose dive of about three hundred feet, then flattened out again, intending to rush the Channel at one hundred and twenty miles an hour, lest they should slip unconsciously into an air-pocket.
As he did so, he noticed a flash of fire followed by a puff of white smoke down at the Castle.
"A signal!" shouted Jock, who had noticed the occurrence at the same instant.
"Yes, they want to speak to us," and with a circling sweep the machine came round as Dastral pulled the joy-stick hard over, and swept back again until he hung right over Dover Castle.
"Can you make it out, old man?" asked the pilot.
"Yes, I have it," cried Fisker, whose eyes had been glued to a spot on the Castle grounds just at the top of the hill overlooking the naval harbour.
"What is it? Do they want us to go down?"
"No. The Commander of the fort says there are several enemy submarines in the Channel, and requests us to keep a sharp look-out for them as we cross over."