Ask anyone who knows, and he will tell you that there is nothing to compare to the zest of the aerial flight. Those contemplating it for the first time view it with mixed feelings of trepidation and anticipation, but once in flight there is only unbounded exhilaration. The experience is like that of throwing off shackles which have bound one to a narrow earthly existence; mere human cares and worries are for the time at least forgotten, and one feels the freedom of the birds and glows with the very pleasure of it. Fears which beset the preliminaries are forgotten; the imagination is awakened with new ambitions; life seems to hold forth previously unthought-of possibilities. And the real joy of it all is that the aerial flight never loses its thrill, never fails in these and new sensations.

Add to this the mystery contained in their unexpected summons to Washington, and the natural pride stirred by the anticipation of being called upon for some important service, and you have some realization of the feelings which animated these four young men as, at a cruising speed of ninety miles an hour, they continued their voyage southward, a mile and a half in the air, two miles out to sea from the shore line, looking like a giant eagle in the sky to those who discovered or discerned them at all.

As for personal comfort, they were as free from the driving wind as though they had been riding in a limousine automobile, for indeed this was a limousine airship, thoroughly enclosed as concerned the Nacelle, or cock-pit and fusilage, which contained the crew and access to every part of the engine, radio, etc.

Occasionally Fred would catch snatches of wireless messages, but mostly they were of a commercial and therefore uninteresting character.

It was about midnight when they came within that sky glow which informed them that they were approaching the metropolis of America—New York.

"Think of the damage a bomber could do, and the consternation it could raise down there," said Don. "Let's circle around two or three times, just for the fun of it. We've got plenty of time now."

And they did. Cutting inland, they crossed almost directly over the heart of the city, continued over the North River and above Hoboken, swung down and around Newark, out over the bay and then upward toward the big city again, as though actually bent upon a mission of mischief.

Again they repeated this, and then swerved out over Brooklyn and above the open sea again.

A little more than an hour elapsed and they were above Philadelphia. It lay like a great black splotch on the ground, the meagre moonlight playing on the Delaware in a way to make it look like a great thread of silver. Only a winding line indicated where the Schuylkill cut the city in two, but where it joined the Delaware the latter began to widen, and from the height of the plane they could see far below to where the river became a bay.

Ships dotted it here and there like little spiders resting on a pool. Nothing moved. It was like a fairy visit to another and a dead world.

The bay itself was so smooth that they decided to drop there for a few minutes, open their thermos bottles of coffee, which was still hot, eat a couple of sandwiches at leisure, and then continue the trip. Finally finding a spot so remote from any ship that it was unlikely that their descent would be discovered, and thereby perhaps raise a furore of excitement and speculation as to who they were and what they were doing there at that queer time, they made their landing with such ease as hardly to cause a splash as they settled on the surface of the water.

The inner man satisfied, they prepared for the continuance of their trip. There was a swift inspection of every part of the plane, and in another ten minutes they were again under way, the firing of the engines sounding like a miniature artillery bombardment on the stillness of the night.

As they rose with the speed and strength and sureness of a giant eagle, they left the city of William Penn far behind, noted the spot which indicated Lewes, Delaware, as it seemed to flit swiftly beneath them on the flank of the lower bay, then passed Cape May and were out over the open sea again. The moon was now disappearing and it devolved upon Don Harlan, the navigator of the crew, by chart and compass and air-speed indicator (whose information, by the way, is always problematical, for reasons which will be explained in a moment), to guide them safely to their destination.

Now as to one of the present grave difficulties with which the navigators of the air have to contend, especially when flying over bodies of water, which, unlike flights over the ground, give no "landmarks" by which position may be determined.

If there is, let us say, no wind whatever blowing, either with or against the direction of the plane, the air-speed indicator will register one hundred miles per hour speed when the plane is traveling at that rate. But let the plane, with its engines running at the same power, get into the teeth of a seventy-five-mile-an-hour gale, and with a seventy-five mile push back to a hundred mile an hour forward push of the engines, the speed-indicator will still register one hundred miles per hour (that is, air-speed), although the plane will actually be traveling a distance of only twenty-five miles per hour with relation to the ground.

In other words, it is the principle of air pressure, and if there is no adverse air pressure, the indicator will show the exact speed of the plane. But the moment the plane is either augmented or retarded by favorable or unfavorable winds, the air-speed indicator becomes a very unreliable instrument for showing distances traveled: it practically only records the speed of the air pushed past the plane. It is like running at ten miles an hour with a pin-wheel in the hand on a perfectly calm day, and getting a certain velocity of revolutions of the wheel per minute. On another day one might stand still with the pin-wheel and permit the rush of a high velocity of wind to twirl it round with the same speed.

And here is a hint to our youthful readers who are interested in mathematics and things mechanical: Sometime somebody is going to invent an instrument which will record an aeroplane's actual speed with relation to the distance covered above the ground; in other words, which will actually show a speed of only twenty-five miles an hour when a hundred-mile-an-hour engine speed is being reduced to twenty-five by a head-on seventy-five-mile-an-hour gale; and the one who succeeds with that invention not only will make for himself a fortune, but then may turn his attention to the devising of another instrument, equally important, which will show how far a side wind is driving a plane out of its course.

But Don Harlan had trained long and studiously to combat and conquer just such difficulties, and like the seasoned sailor who can look at a clear sky and seem to smell a storm brewing, or a squall coming, he had learned, by some intuition which he could not even attempt to explain, to estimate with almost miraculous accuracy to just what extent the wind was retarding them or blowing them off their course.

He was bending over his charts now, marking off their course, registering the slight wind deviation, when an exclamation from Fred, who sat at all times with the radio earpieces on, attracted the attention of all. With Big Jack and Andy Flures, the pilots, it was indicated merely by the briefest turning of the head, but Don stopped short in his work to watch Fred jotting down a message that was coming mysteriously out of the night.

"Official dispatch," he announced a moment later.

"Follow previous instructions. One remain with plane, other three at my office nine if possible. Repeat."

It was signed by Bronson, head of the air service.

Fred threw on the switch of the radio and opened up with the code call. Almost immediately he got a response. He repeated the message, and then gave their approximate location as Don had plotted it out.

There was a considerable delay, during which they concluded that the dispatch was being telephoned to General Bronson, and then the answer came, "Good work," and out of the silence of the night there was recorded no more.

The balance of their journey was without incident, but every turn of the propeller, every explosion within the cylinders, it might be said, gave them renewed confidence that when they essayed the ocean flight, if that should be their privilege or their mission, they would do so with a machine as near to perfection as modern engineering could make it.

It was hardly dawn when they settled on the surface of the Potomac, and, with the time still left them made a cursory overhauling of their engine in search of any weaknesses or defects. They found none. It was as though the long trip from Halifax to Washington had been merely a warming-up, preliminary to some real test of staunch durability.

It was immediately and amicably decided that Fred, because of his knowledge of the wireless, which might catch some message relating to their disappearance from Halifax and thus tell them what was being speculated about them, should remain with the plane, while the other three changed into the presentable "cits," or civilian clothes, they had brought with them, and carry out the balance of the instructions concerning meeting General Bronson at nine o'clock at his office.

We know what they were to be told, and it did not take General Bronson, a man noted for his brevity, long to impart to them the fact that they were to undertake a mission which, considered in all its phases, was absolutely without precedent.

"We will now go and meet the members of the Cabinet," he said.

In fifteen minutes they were in the presence of the men who had directed the various services of the Government during the greatest war in the world's history. They were introduced, most critically looked over, and asked a few, but a very few, questions. Then the Assistant Secretary of State gave them their final instructions.

"You understand thoroughly the importance of these papers?" he asked.

"Absolutely, sir," Big Jack replied, and the other two nodded affirmatively.

"Very well, then," the Assistant Secretary of State replied. "The continued peace of the world may hinge upon your success. There must be no failure. You will guard these papers with your lives. I hand them to you in the presence of the members of the Cabinet. Deliver these at Paris."