unpleasant surprises often occur.

Many a U-Boat commander has thought it possible with a certain amount of excess weight to submerge without difficulty and to keep his boat at a fixed depth. Suddenly, however, the pressure gauge registers a greater depth and the boat drops in the water, like an aeroplane which has fallen into an air-pocket, until a test of the specific weight and temperature of the water gives the clue to her behaviour.

It will therefore be seen that such measurements are necessary before the commander can count with certainty on being able suddenly to submerge and as suddenly to reappear above the waters.

In the meantime we have finished our submerging test satisfactorily. All has gone well and each part fully performed its functions. We are in complete control of our complicated apparatus.

Now the command to reappear is given, the diving rudders are set to "up," and immediately I am able by the depth gauge to follow their working and that of our stout pumps.

After assuring myself that there is no noise of propellers to be heard anywhere in our vicinity, and that on all sides there is no likelihood of collision with any steamer, we pass through the dangerous "blind moment."

By this I mean that space of time during which the boat has risen so high that she could be rammed; while, on the other hand, she is still too deep under the water to get the periscope above the surface and take a look round.

This lasts a few minutes. I stand at the periscope and watch. Already the field of vision is lighter. Silvery air bubbles rise up glittering; a blinking and twinkling appears on the glass. Then it is day. A picture arises, clear and shining. The North Sea sways before my eyes with an empty and endless horizon.

Now we are rising to the surface. By the use of the rudder the boat pushes forward faster and faster to the surface of the water. In order to accelerate the ascent compressed air is forced into one of the submersion tanks.

Now she moves very rapidly: the tower is already free. The deck rises dripping out of the water, the conning-tower hatch is opened, fresh air streams in, and I give the command:

"Blow out ballast tanks!"

A wild howling and screeching comes in reply from the control-room, while the powerful turbine engine presses the water out from the submerging tanks.

This does not take long. As soon as a tank is empty the excess air rushes out with a pleasant sound at the side of the boat, and we are soon in normal floating trim again.

We are still using electricity. Now comes last of all the starting up of the heavy Diesel engines by the electric motors.

I have already climbed into the conning-tower and can see nothing of all this, except by the communications from the control-room. Those who are in the engine-room, however, will have an exciting spectacle.

The observation engineers stand at their posts. A command comes through the speaking-tube. Everything is ready. Then the chief engineer gives a shrill whistle, raises his hand, two quick wrenches at the switchboard in the electrical engine-room, a couple of blinding flashes half an inch long: the first valve-heads rise slowly, hesitatingly, as if unwilling, then quicker, a wild report and hissing, a wild irregular spluttering, then the loud explosions become rhythmical, and faster and faster both machines resume their regular vibrations.

The submerging test is completed, and pounding along the "Deutschland" proceeds on her way. The wind does not drop, but the weather keeps fine and the visibility is good.

No steamer comes in sight: we can remain comfortably above water. Nevertheless we need to be extremely careful in our navigation.

So the day draws to its end. But as the sun sinks, dark threatening clouds appear, prophesying bad weather for the following day.

CHAPTER IV
THE U-BOAT TRAP

And thus it turns out. The further we get from land, the rougher grows the sea. The boat is badly tossed about. I notice the roughness of the sea as I lie in my cabin, and towards two o'clock in the morning I am awakened by a "Hullo," from the speaking-tube on the wall at my head.

The watchful second officer, Eyring, announces a white light to starboard which is approaching rapidly.

I spring out, balancing myself round the corner in the control-room, over the ladders, up through the conning-tower hatch, on to the platform.

Eyring shows me at no great distance ahead a white light. It appears to be approaching. We decide not to let it come any nearer, and give the alarm to submerge. Then for the first time I realise the wonderful sense of security that the possibility of such a rapid submersion gives.

It is all quite a matter of course. Here we travel in the middle of this world-war, with an unarmed freight vessel through darkest night. A light approaches. It may be an enemy, it probably is. In a few minutes a couple of shots may flash out, several shells shatter our conning-tower, the water stream into the ship's body, and in a short while the North Sea close over us.

None of this occurs however. A brief command in the control-room, a few grips of the valves and hand wheels, and we continue our way unhurt, for brutal power may shut us from the surface of the seas, but our enemies in their impotence only cause us to lie a few fathoms deeper. We continue submerged for the sake of safety until daybreak. Towards four o'clock we rise to the surface. It is already broad daylight, but unfortunately also there is a very troubled sea. In the distance we see a couple of fishing-boats laboriously going about their business. We keep them at first sharply under inspection, but quickly discover their harmless character and continue our way over the water.

This process has long ceased to be of a pleasant character. The movements of the boat are such that existence down below in the closed-up compartments, aired only by the ventilator machines, is causing headache and sickness among the men; part of the crew are losing their appetites. Yet it is quite out of the question to remain on deck, which is continuously swept by the seas.

It is somewhat drier on the conning-tower behind the shelter of the "bath-tank" and on the lee side of the tower, which is sheltered from the sea and wind.

Here a few of the watch off duty are huddled together, holding fast to the rails, inhaling the fresh air and shaking themselves when a particularly heavy breaker rolls up round the conning-tower covering them in salt spray.

Thus we travel on the whole day.

A couple of steamers, whose smoke-clouds appear in the distance, we avoid above water by altering our course, after we have made out their route by careful sounding and observation.

This sounds more difficult than it really is. You first of all make sure of the position of your own ship by soundings and calculations, after you have roughly estimated the position of the unknown vessel on the map. If the relative positions of these two are compared on the map with the most important steamer routes, it is possible to judge with some certainty the course the unknown ship must take.

Such a calculation was soon to prove of great importance to us, and was in this case, as will be seen, of great significance.

Towards evening it clears up slightly, and the sea grows calmer. The sun sets under brilliantly illuminated clouds in the west.

All the watch off duty have come on deck to get some fresh air and smoke a hasty cigar or cigarette. Below deck smoking is strictly forbidden. The men are all huddled together on the sheltered side of the conning-tower, tightly packed and pressed against the wall.