"A pressure cooker?"

"Looks like it, doesn't it? This is our garbage-disposal unit. In the old days, when a submarine had to surface every few hours, garbage disposal was no problem: you just tipped the stuff over the side. But when you spend weeks on end cruising at three hundred feet, you can't just walk up to the upper deck and tip the waste over the side: garbage disposal becomes quite a problem. This tube goes right down to the bottom of the «Dolphin». There's a heavy water-tight door at the lower end corresponding to this one, with interlocking controls that make it impossible for both doors to be open at the same time: it would be curtains for the «Dolphin» if they were. Sam here, or one of his henchmen, sticks the garbage into nylon mesh or polythene bags, weighs them with bricks — "

"'Bricks,' you said?"

"Bricks. Sam, how many bricks aboard this ship?"

"Just over a thousand at the latest count, Doc."

"Regular builder's yard, aren't we?" Benson grinned. "Those bricks are to make sure the garbage bags sink to the bottom of the sea and not float to the surface. Even in peacetime we don't want to give our position away to anyone. In go three or four bags, the top door is clamped shut, and the bags are pumped out under pressure. Then the outer door is closedagain. Simple."

"Yes." For some reason or other this odd contraption held a curious fascination for me. Days later I was to remember my inexplicable interest in it and wonder whether, after all, I wasn't becoming psychic with advancing years.

"It's not worth all that attention," Benson said goodhumoredly. "Just an up-to-date version of the old rubbish chute. Come on, a long way to go yet."

He led the way from the galley to a heavy steel door set in a transverse bulkhead. Eight massive clamps to release and then replace after we had passed through the doorway.

"The for'ard torpedo storage room." Benson's voice was lowered, for at least half of the sixteen or so bunks that lined the bulkheads or were jammed up close to the torpedoes and racks were occupied and every man occupying them was sound asleep. "Only six torpedoes, as you can see. Normally there's stowage for twelve plus another six constantly kept loaded in the torpedo tubes. But those six are all we have just now. We had a malfunction in two of our torpedoes — the newest and more or less untested radio-controlled type — during the Nato exercises just ended, and Admiral Garvie ordered them all to be removed for inspection when we got back to the Holy Loch. The «Hunley» — that's our depot ship — carries experts for working on those things. However, they were no sooner taken off yesterday morning than this driftstation operation came our way, and Commander Swanson insisted on having at least six — of them put back on right away." Benson grinned. "If there's one thing a submarine skipper hates it's putting to sea without his torpedoes. He feels he might just as well stay at home." -

"Those torpedoes are still not operational?"

"I don't know whether they are or not. Our sleeping warriors here will do their best to find out when they come to."

"Why aren't they working on them now?"

"Because before our return to the Clyde, they were working on them for nearly sixty hours non-stop trying to find out the cause of the malfunction — and if it existed in the other torpedoes. I told the skipper that if he wanted to blow up the «Dolphin», as good a way as any was to let those torpedomen keep on working — they were starting to stagger around like zombies, and a zombie is the last person you want to have working on the highly complicated innards of a torpedo. So he pulled them off."

He walked the length of the gleaming torpedoes and halted before another steel door in a cross bulkhead. He opened this, and beyond, four feet away, was another such heavy door set in another such bulkhead. The sills were about eighteen inches above deck level.

"You don't take many chances in building those boats, do you?" I asked. "It's like breaking into the Bank of England."

"Being a nuclear sub doesn't mean that we're not as vulnerable to underwater hazards as the older ships," Benson said. "We are. Ships have been lost before because the collision bulkhead gave way. The hull of the «Dolphin» can withstand terrific pressures, but a relatively minor tap from a sharpedged object can rip us wide open like an electric can opener. The biggest danger is surface collision, which nearly always happens at the bows. So, to make doubly sure in the event of a bows collision, we have those double-collision bulkheads — the first submarine ever to have them. Makes fore and aft movement here a bit -difficult, but you've no idea how much more soundly we all sleep at night."

He closed the after door behind him and opened the for'ard one. We found ourselves in the for'ard torpedo room, a narrow, cramped compartment barely long enough to permit torpedoes to be loaded or withdrawn from their tubes. Those tubes, with their heavy hinged rear doors, were arranged close together in two vertical banks of three. Overhead were the loading rails, with heavy chain tackles attached. And that was all. No bunks in here and I didn't wonder: I wouldn't have liked to be the one to sleep for'ard of those collision bulkheads.

We began to work our way aft and had reached the mess hail when a sailor came up and said that the captain wanted to see me. I followed him up the wide central stairway into the control room, Dr. Benson a few paces behind to show that he wasn't being too inquisitive. Commander Swanson was waiting for me by the door of the radio room.

"Morning, Doctor. Sleep well?"

"Fifteen hours. What do you think? And breakfasted even better. What's up, Commander?" Something was up, that was for sure: for once, Commander Swanson wasn't smiling.

"Message coming through about Drift Station Zebra. Has to be decoded first, but that should take only minutes." Decoding or not, it seemed to me that Swanson already had a fair idea of the content of that message.

"When did we surface?" I asked. A submarine loses radio contact as soon as it submerges.

"Not since we left the Clyde. We're close to three hundred feet down right now."

"This is a «radio» message that's coming through?"

"What else? Times have changed. We still have to surface to transmit but we can receive down to our maximum depth. Somewhere in Connecticut is the world's largest radio transmitter, using an extremely low frequency, which can contact us at this depth far more easily than any other radio station can contact a surface ship. While we're waiting, come and meet the drivers."

He introduced me to some of his control-center crew — as with Benson, it seemed to be a matter of complete indifference to him whether it was officer or enlisted man — and finally stopped by an officer sitting just aft of the periscope stand, a youngster who looked as if he should still be in high school. "Will Raeburn," Swanson said. "Normally we pay no attention to him but after we move under the ice he becomes the most important man on the ship. Our navigation officer. Are we lost, Will?"

"We're just there, Captain." He pointed to a tiny pinpoint of light on the Norwegian Sea chart spread out beneath the glass on the plotting table. "Gyro and sins are checking to a hair."

"'Sins'?" I said.

"You may well look surprised, — Dr. Carpenter," Swanson said. "Lieutenant Raeburn here is far too young to have any sins. He is referring to S.I.N.S. — Ship's Inertial Navigational System — a device once used for guiding intercontinental missiles and now adapted for submarine use, specifically nuclear submarines. No point in my elaborating: Will's ready to talk your head off about it if he manages to corner you." He glanced at the chart position. "Are we getting there quickly enough to suit you, Doctor?"