The world beneath them was waking up now, for the two aviators could see the smoke ascending from the chimneys of a few scattered farmhouses and cottages. The birds, too, were astir, and the larks, mounting up towards the sun, made sweet music which was drowned in the whir-r-r of that strange-looking bird of prey, which sailed serenely above them. Instinct, however, made the songsters shrink and flee away from that hawk-like menace with stretched-out wings, for they evidently feared that it might swoop down upon and destroy them. "Dover!" shouted the observer suddenly, as the Cinque Port came into view. "Yes, by Jove! So it is. I hope they won't turn the guns of the fort upon us." "No fear. They'll have been warned of our coming by now." A minute later, they opened out the sea, the forts, and Shakespeare's Cliff, and within another three minutes they had crossed the boundary of sea and land, and at a tremendous altitude were gliding over the Channel. "Nine thousand!" yelled Dastral, turning his head towards Jock, after casting a brief glance at his indicator. "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." "Cheery-o, Jock! That's good news. I'm going to drop down a bit, then. There's a D.S.O. for you if you spot one. Here goes!" And with that, Dastral jammed over the controls again, and did a neat nose dive of two thousand feet, looping the loop once or twice just to express his joy, and give vent to his feelings. Jock had picked up this information from a few white strips of calico, which had been stretched out in a curious fashion within the Castle grounds. To a trained observer like Fisker, it was mere child's play to read a code signal like that.