from Delhi, adding merely:–
"Do you think it possible?"
"Scarcely," replied Keane carefully, "but with a master mind like this, one never knows. It will be necessary for you to consult the most eminent professors of science and chemistry at once."
"I intend to visit Professor Verne at his house first thing to-morrow, or rather to-day, for it is already morning."
"But the aeroplane," added Sharpe, who had been perusing the Delhi message, "this also must have been specially built for this new gas."
"Given the one, the other would naturally follow, and would be the lesser task of the two, for this man is a great engineer as well," said Keane.
"It is a deep well of mystery," continued Tempest after another pause; "but something must be done at once. To-morrow the morning papers will be full of it. Next day Parliament meets, and questions will be asked, and it will all come upon us. I shall have to meet the Home Secretary as soon as I have interviewed Professor Verne, and Lord Hamilton will not be easily satisfied. The public will also be clamouring for information on the subject, and they will have to be appeased and calmed. The Stock Exchange will begin to talk also, and to demand compensation for the companies whose properties have been damaged. Insurance rates, marine and otherwise, will be raised, and Lloyd's underwriters will not fail to make a fuss. Now, gentlemen, what steps can we take to deal with these raiders in the immediate future?"
Send us after this mystery 'plane on fast scouts with plenty of machine-gun ammunition," urged Sharpe.
"I cannot spare you for that, but I have already ordered strong patrols of aerial police to search for the brigands. I must have you here or somewhere within call. At any rate, I cannot let you go further than Germany. It may be necessary to send you there again."
"On what account, sir?" asked Keane.
"To find the aerodrome which this raider calls 'home,' for he must have a rendezvous somewhere if only to obtain supplies and repairs."
"And that secret aerodrome must be somewhere in Germany, hidden away in some out-of-the-way place," ventured Sharpe.
"But in what part of Germany?" asked the commissioner.
"Let me see," cried Keane, rising to his feet, and walking across the room to where the large map of Germany hung upon the wall–"why, it must be in the Schwarzwald!"
"The Schwarzwald!" exclaimed the other two.
"Yes, it is by far the best hiding-place in the whole country. One may tramp for days and never see a soul. It must be somewhere in the Schwarzwald."
"Then to the Schwarzwald you must go to-morrow, adopting whatever disguises you desire, and you must find this hidden spot where the conspiracy has been hatched," concluded the colonel.
CHAPTER V
THE AERIAL LINER
The airship liner, Empress of India, was preparing to leave her moorings, just outside the ancient city of Delhi, for Cairo and London. This mammoth airship was one of the finest vessels which sailed regularly from London, east and west, girdling the world, and linking up the British Empire along the All-Red Route. She had few passengers, as she carried an unusually heavy cargo of mails for Egypt and England, and a considerable amount of specie for the Bank of England. Several persons of note, however, figured amongst her saloon passengers, including the Maharajah of Bangapore, an Anglo-Indian judge, and a retired colonel of the Indian army.
She was timed to depart at mid-day, and during the morning mailplanes had been arriving from every part of India with their cargoes of mail-bags, already sorted for the western trip.
The great mammoth now rode easily with the wind, moored by three stout cables to the great tower which rose above the roof gardens of the air-station. An electric lift conveyed the passengers and mails to the summit of this lofty tower, from whence a covered-in gangway led to the long corridors which lined the interior of the rigid airship.
"Have all the engines been tested?" the captain asks of the chief engineer, as he comes aboard with his navigating officer.
"Yes, sir."
"All the passengers aboard?" he asks next of the ground officer.
"All except the maharajah, Captain, and I expect him any moment."
"Excellent," replied the skipper. "There's a good deal of bullion aboard from the Indian banks, I hear, and the rajah himself is likely touring a lot of valuables with him, I understand, as he is to attend several court functions at St. James's Palace."
"Yes, sir. I hope you won't meet that aerial raider," replied the ground officer.
"Poof! What can he do? He can't board us in mid-air! Besides, I hear that the aerial police are on his track, and that all their fast scouts are patrolling the mail routes."
"Yes, you'll have an aerial escort with you for the first two hundred miles, Captain. They'll pick you up shortly after you leave here."
"Absolutely a waste of time. The police could be much better employed in searching for these rascals."
"Well, perhaps you're right," replied the ground official. "They certainly cannot board you in mid-air, as you observe, and they cannot set you on fire as they did the early Zeppelins, for helium won't burn."
This conversation was interrupted by shouts and cheers which reached the speakers from down below.
"Hullo! here comes the rajah. I must go down and welcome him," said the captain, as a fanfare of trumpets announced the arrival of the great Indian chief.
Then, with all the ceremonial and pomp of the East, the Maharajah of Bangapore was welcomed aboard the luxurious air-liner, and, accompanied by his personal attendants, he was shown with much obsequiousness to his private saloon. His baggage, containing treasures worth a king's ransom, was likewise transferred, under the supervision of his chamberlain, from the ground to his suite of apartments.
The clock in the palace of the Great Mogul in the old city of Delhi strikes twelve, and the captain's voice is heard once more, as he speaks from the rear gondola:–
"All ready?"
"Yes, sir, all clear!"
A button is pressed and the water ballast tanks discharge their cargo to lighten the ship, and then swiftly comes the final order:–
"Let go!"
And as the cables are slipped from the mooring tower, the light gangway is drawn back, the crowd down below cheer, and the giant airship backs out, carried by the force of the wind alone till she is well clear of the station. Then her engines open up gradually. She turns until her nose points almost due west, then slips away on her four thousand miles' journey over many a classic land, desert, forest and sea towards the centre of the world's greatest empire.
About four o'clock that afternoon, as Judge Jefferson sat and talked with his friend Colonel Wilson in one of the rear gondolas where smoking was permitted, he remarked that this was his seventh trip home to England by the aerial route, and declared that he could well spend the rest of his lifetime in such a pleasant mode of travel.
"There's no fatigue whatever," he added; "nothing of the jolt and jar which you get in the railway carriage. As for the journey by sea, I was so ill during my last voyage that I simply couldn't
