first sight he had of the face of Lieutenant Larson, after the latter had removed his protecting helmet and goggles, made Dick say to himself:

"That fellow will bear watching! I don't like the look in his eyes."

But Dick said nothing of this to Paul or Innis. He made up his mind he would learn their impressions later.

"We thought we might as well come on in the machines, as to have them taken down, shipped here, and then have to assemble them again, would take too much time," went on Captain Grantly. "Though we expect, later, to give your students a practical demonstration in how the biplanes are put together, so they may understand something of how to make repairs.

"We came on from the nearest army aviation grounds, and had a most successful flight. I must send back word to Major Dalton."

"Our telephone, or telegraph service, is at your disposal," said Colonel Masterly. "If you will come with me—"

"Excuse me, but we carry with us our own means of communication," said Captain Grantly with a smile. "We are going on the assumption, constantly, that we are in an enemy's country.

"Consequently we go prepared as though there were a state of war. We shall communicate with our base by means of wireless."

"I am afraid we can't accommodate you there," went on the head of the military school. "We are installing a wireless outfit, but it is not yet completed," the colonel said.

"Oh, we carry our own!" was the unexpected retort. "Lieutenant Larson, if you and Lieutenant McBride will get the balloon ready, Captain Wakefield and myself will work out the cipher dispatch, and send it.

"We use a code in our wireless," he went on to explain, "and it takes a few minutes to make up the message."

"But I heard you speak of a balloon," said Colonel Masterly. "I don't see how you carry one on your machine."

"Here it is," was the answer, and a deflated rubberized silk bag was produced from a locker back of the pilot's seat. "This is the latest idea in airship wireless," went on Captain Grantly, as he directed the lieutenants to get out the rest of the apparatus. "We carry with us a deflated balloon, which will contain about two hundred cubic yards of lifting gas. The gas itself, greatly compressed, is in this cylinder. There's enough for several chargings.

"We fill the balloon, and attach to it our aerial wires. The balloon takes them up about four hundred feet—the wires weigh about twenty pounds, I might say. Then we carry a light sending instrument. It has a considerable range, though we can receive messages from a much greater distance than we can send, as our force for a sending current is limited."

As he was talking the others were working, and the cadets looked on interestedly. The drill had been abandoned, and officers and students crowded up near the army aviators to see what was going on.

With a sharp hiss the compressed gas rushed from the containing cylinder into the deflated balloon. The silken sides puffed out, losing their wrinkles. The balloon gradually assumed larger proportions.

"Ready with the wires?" asked Captain Grantly.

"All ready, sir," replied Lieutenant Larson. Dick now heard him speak for the first time, and did not like his voice. There are some persons who make a bad impression on you at the first meeting. Often this may he unjustified, but Dick's first impressions were seldom wrong.

The wires, forming the wireless aerial, were carried up on two light spreaders, hanging down from a network that went over the balloon bag. From the aerials depended the wires that were attached to the receiving and sending apparatus. These wires were on a reel, and would he uncoiled as the balloon arose. The earth-end would be attached to the telephone receivers and to the apparatus, consisting of a spark-gap wheel and other instruments designed to send into space the electrical impulses that could be broken up into dots, dashes and spaces, spelling out words according to the Morse or Continental code—whichever was used.

Captain Grantly looked over everything. His assistants signified that every connection was made.

"Send her up," ordered the commander, and as the catch, holding the balloon, was released the spherical bag of gas shot into the air, carrying with it the aerials, and unreeling the connecting wires.

Quickly it rose to nearly five hundred feet, and, when it had been anchored, all was soon in readiness.

Meanwhile a code dispatch had been written out, and as it was handed to Captain Wakefield, who was to operate the wireless, he began depressing the key that made and broke the electrical current. The current itself came from a small, but powerful, storage battery, and it had been switched on. The current also set in motion a toothed wheel of brass. This wheel revolved on its axis with the points, or teeth, passing rapidly in front of a platinum contact point.

As each tooth thus came in opposition to the point, a blue spark of electricity would shoot out with a vicious snap; that is if the connection key were pressed down. If the key were not depressed no current flowed.

I presume most of you understand how the wireless works, so I will not give you a complete description save to say that it is just like a telegraph system, in fundamentals. The only difference is that no connecting metallic wires are needed between stations.

A group of wires in parallels, called "aerials," are hung in the air at one point, or station, and a similar set is suspended at the other station. The electrical current jumps through the air from one group of wires to the other, without being directly connected, hence the name "wireless," though really some wires are used.

The electrical impulse can be sent for thousands of miles through the air, without any directly connecting wires. And the method of communication is by means of dots, dashes and spaces.

You have doubtless heard the railroad or other telegraph instruments clicking. You can hold your table knife blade between two tines of your fork, and imitate the sound of the telegraph very easily.

If you move your knife blade up and down once, quickly, that will represent a dot. If you move it more slowly, holding it down for a moment, that would be a dash. A space would be the interval between a dot and a dash, or between two dots or two dashes.

Thus, by combinations of dots, dashes and spaces, the letters of the alphabet may be made and words spelled out. For instance a dot and a dash is "A."

In telegraphing, of course, the operator listens to the clicking of the brass sounder in front of him on the desk. But in wireless the electrical waves, or current received, is so weak that it would not operate the sounder. So a delicate telephone receiver is used. This is connected to the receiving wires, and as the sender at his station, perhaps a thousand miles away, presses down his key, and allows it to come up, thus making dots, dashes and spaces, corresponding clicks are made in the telephone receiver, at the ear of the other operator.

It takes skill to thus listen to the faint clicks that may be spelled out into words, but the operators are very skillful. In sending messages a very high tension current is needed, as most of it is wasted, leaping through the air as it does. So that though the clicks may sound very loud at the sending apparatus, and the blue sparks be very bright, still only faint clicks can be heard in the head-telephone receiver at the other end.

"You may send," directed Captain Grantly to Captain Wakefield, and the blue sparks shot out in a dazzling succession, as the spiked wheel spun around. This was kept up for some little time, after the receiving operator at the army headquarters had signified that he was at attention. Then came a period of silence. Captain Wakefield was receiving a message through space, but he alone could hear this through the telephone receiver.

He wrote it out in the cipher code, and soon it was translated.

"I informed them that we had