side with a current of warm air passing up and down the tube. We can raise and lower the periscopes at will. All our larger boats have two of them, so that they can keep a lookout in two directions at once, besides having a spare eye in case the first is put out."

"What are those two little things that big naval tug is towing over there?" I inquired.

"The target for our torpedo practice," replied Lieutenant Scope. "We shall try to put four Whiteheads between those two buoys as the tug tows them past at an unknown range and speed. If you step forward to the torpedo-room you can see the crew loading the tubes."

Stripped to the waist like an old-time gun-crew, four beautifully muscled gunner's mates, with an ingenious arrangement of chains and pulleys, were hoisting a torpedo from the magazine. The breach of the tube was opened and the long Whitehead thrust in, two flanges on its sides being fitted into deep grooves in the sides of the tube, so that the torpedo would not spin like a rifle-bullet but be launched on an even keel. The breach was closed, and the men stood by expectantly.

"The skipper is up in the conning-tower, taking aim through the periscope," explained the man who had told me about trimming-tanks. "The tubes being fixed in the bow, he has to train the whole boat like a gun. Likewise he must determine how far it is to the target and how fast the tug is towing it, how many seconds the torpedo will take to get there, and how much he must allow for its being carried off its course by tide and currents. When he gets ready, the lieutenant will press a little electric button and you'll hear

"THUD!" went the compressed air in the tube, and the submarine shuddered slightly with the shock of the recoil. But that was all.

"There she goes!" said my friend the tank-expert, as soon as the Whitehead was expelled.

Four of the ten torpedoes carried in the magazine were sped on their way to the unseen target. I returned to the turret as the wireless operator entered and handed a typewritten slip to Lieutenant Scope, who smiled happily and said to me:

66

'The captain of the tug reports that all four shots were hits and all four torpedoes have been safely recovered."

I was too astonished to congratulate him on his marksmanship, as I should have done.

"How in the name of miracles," I gasped, "can you receive a wireless telegram under the sea?"

"By the Fessenden oscillator," he replied, and added to the wireless man, "Take this gentleman below and show him how it works."

"Did you ever have another chap knock two stones together under water when you were taking a dive?" asked the operator. I nodded in vivid recollection.

"Then you have some idea how sounds are magnified under water. It is an old idea to put submarine bells down under lighthouses and fit ships with some kind of receiver so that the bells can be heard and warning given when it is too foggy to see the light. The advantage over the old-style bell-buoy lies in the fact that sound travels about four times as fast through water as through air, and goes further and straighter because it isn't deflected by winds or what the aviators call 'air-pockets.'

"Fastened outside the hull of this boat is one of the Fessenden oscillators: a steel disk eighteen inches in diameter, that can be vibrated very rapidly by electricity. These vibrations travel through the water, like wireless waves through the ether, till they strike the oscillator on another vessel and set it to vibrating in sympathy. To send a message, I start and stop the oscillator with this key so as to form the dots and dashes of the Morse code. To receive, I sit here with these receivers over my ears and ‘listen in,' just like a wireless operator, till I pick up our call 'X-4,' "X-4.""

"How far can you send a message under water?"

"Ten miles is the farthest I've ever sent one."

"Even now, couldn't a surface vessel act as eyes for a whole flotilla of submarines and tell them where to go and when to strike by coaching them through the Fessenden oscillator?" The operator nodded.

"We're doing it to-day, in practice. But don't forget that an enemy's ship carrying a pair of oscillators can hear a submarine

coming two miles away. They can make out the beat of a propeller at that distance every time."

"But how can you tell how far away and in what direction the boat is?"

"I can't, with a single oscillator like ours. But a ship carries two of them, one on each side of the hull, like the ears on a man's head. Just as a man knows whether a shout he hears comes from the right or left, because he hears it more with one ear than the other, so the skipper of a surface craft can look at the indicator that registers the relative intensity of the vibrations received by the port and starboard oscillators and say,

"There's somebody three points off the starboard bow, mile and three quarters away, and heading for us. Nothing in sight, so it must be one of those blamed submarines.'

"And away he steams, full speed ahead and cutting zigzags. Or maybe he gets his rapid-fire guns ready and watches for Mr. Submarine to rise as the X-4's doing now."

Freed of the dead weight of many tons of sea water blown from her ballast-tanks by compressed air, the submarine rose to the surface like a balloon. Ventilators and hatch-covers were thrown open and we swarmed up on deck to fill our grateful lungs with the good sea air. Three motor-boats from the tug throbbed up alongside with the four torpedoes we had discharged.

"Those boats wait, one this side of the target, one near it and the third over on the far side, to mark the shots and catch the torpedoes after they rise to the surface at the end of their run," said Lieutenant Scope. "We very seldom lose a torpedo nowadays. They tell a story about one that dived to the bottom and was driven by the force of its own engines into forty feet of soft mud, where it stayed till it happened to be dug up by a dredger."

The four torpedoes were hoisted aboard, drained of the sea water that had flooded their air-chambers, cleaned and lowered through the torpedo hatch forward down into the magazine. By this time the bridge and railing were again in place and the flags fluttering over the taffrail as the X-4, her day's work done, sped swiftly up the coast to home and mother-ship.

CLASS ACTIVITIES

1. Study: To test the thoroughness of your reading see how many of the following questions you can answer. Look up the ones that

bother you.

a. How does the Diesel engine operate?

b. How does its operation differ from the operation of a gasoline engine?

c. Why is it necessary to pump water into the tanks as the submarine is about to submerge?

d. How does the pumping of the water help when the boat is coming to the surface?

e. Why is 150 feet a great depth for a submarine?

f. How can one see through a periscope?

g. How do the oscillators enable the crew to detect the direction of a distant ship?

h. Why must a match not be lighted on a submarine?

i. How are the torpedoes aimed when the ship is submerged?

j. How are the wireless messages sent and received when the ship is under water?

2. Final review: Go over the ten questions again making sure you can answer each correctly, reading parts of the article as before, if necessary.

3. Examine the outline below, and determine which of the three ways of putting ideas together is used by Farnham.

THREE WAYS OF PUTTING IDEAS TOGETHER

4. Which order is followed in "Laying the Atlantic Cable,” p. 449?; in The First Railroad Across the Continent," p. 410?

6. SEA-FEVER

JOHN MASEFIELD

As you read, think of the tossing of the waves, and the "roll" of the ocean, as the waves approach the shore. When you read the verses aloud, try to suggest the movement of the waves.

I must down to the seas again, to the lonely sea and the sky,
And all I ask is a tall ship and a star to steer her by;

And the wheel's kick and the wind's song and the white sails shaking,

And a gray mist on the sea's face, and a gray dawn breaking.

I must down to the seas again, for the call of the running tide
Is a wild call and a clear call that may not be denied;
And all I ask is a windy day with the white clouds flying,
And the flung spray and blown spume, and sea-gulls crying.

I must down to the seas again, to the vagrant, gypsy life;
To the gull's way and the whale's way where the wind's like a
whetted knife;

And all I ask is a merry yarn from a laughing fellow-rover

And a quiet sleep and a sweet dream when the long trick's over.

CLASS ACTIVITIES

Here is a list of sea poems. Read as many as you can find. Select three passages from the poems you read which give you good pictures of the sea. In each poem you read, determine whether the sea is loved or feared. Report during General Review, p. 487, No. 5.