Craig laughed. "Walter, you are indeed learning many strange things.
You can't whistle in compressed air.
I was too chagrined to answer. First it was Capps; now it was my own friend Kennedy chaffing me for my ignorance. I was glad to see Paddy's huge form looming in the semi-darkness. He had seen that we were gone and hurried after us.
"Won't ye stay down an' see some more, gintlemen?" he asked. "Or have ye had enough of the air? It seems very smelly to me this mornin' - I don't blame ye. I guess them as doesn't have to stay here is satisfied with a few minutes of it."
"No, thanks, I guess we needn't stay down any longer," replied Craig. "I think I have seen all that is necessary - at least for the present. Capps has gone out ahead of us. I think you can take us out now, Paddy. I would much rather have you do it than to go with anybody else."
Coming out, I found, was really more dangerous than going in, for it is while coming out of the that men are liable to get the bends. Roughly, half a minute should be consumed in coming out from each pound of pressure, though for such high pressures as we had been under, considerably more time was required in order to do it safely. We spent about half an hour in the air-lock, I should judge.
Paddy let the air out of the lock by turning on a valve leading to the outside, normal atmosphere. Thus he let the air out rapidly at first until we had got down to half the pressure of the tunnel. The second half he did slowly, and it was indeed tedious, but it was safe. There was at=20first a hissing sound when he opened the valve, and it grew colder in the lock, since air absorbs heat from surrounding objects when it expands. We were glad to draw sweaters on over our heads. It also grew as misty as a London fog as the water-vapour in the air was condensed.
At last the hiss of escaping air ceased. The door to the modern dungeon of science grated open. We walked out of the lock to the elevator shaft and were hoisted up to God's air again. We gazed out across the river with its waves dancing in the sunlight. There, out in the middle, was a wreath of bubbles on the water. That marked the end of the tunnel, over the shield. Down beneath those bubbles the sand-hogs were rooting. But what was the mystery that the tunnel held in its dark, dank bosom? Had Kennedy a clue?
"I think we had better wait around a bit," remarked Kennedy, as we sipped our hot coffee in the dressing-room and warmed ourselves from the chill of coming out of the lock. "In case anything should happen to us and we should get the bends this is the place for us, near the medical lock, as it is called - that big steel cylinder over there, where we found Orton. The best cure for the bends is to go back under the air-recompression they call it. The renewed pressure causes the gas in the blood to contract again, and thus it is eliminated - sometimes. At any rate, it is the best-known cure and considerably reduces the pain in the worst cases. When you have a bad case like Orton's it means that the damage is done; the gas has ruptured some veins. Paddy was right. Only time will cure that."
Nothing happened to us, however, and in a couple of hours we dropped in on Orton at the hospital where he was slowly convalescing.
"What do you think of the case?" he asked anxiously.