The body of the cylinder would be filled almost to the top with water. The flame boiled the water. The resulting steam went out of the top under its own fierce pressure in a pipe which — I followed it with my eye — led into a large yellow-painted round-ended cylinder slung horizontally near the ceiling. This tank looked rather like a zeppelin. It was, if I remembered right, a calorifier. Inside it, the steam pipe ran in a spiral, like an immobile spring. The tank itself was supplied direct from the mains with the water which was to be heated, the water going to the central heating radiators, and to the hot taps in the kitchen, the cloakrooms and the jockeys’ washrooms. The scorching heat from the spiral steam pipe instantly passed into the mains water flowing over it, so that the cold water entering the calorifier was made very hot in the short time before it left at the other end.
The steam, however, losing its heat in the process, gradually condensed back into water. A pipe led down the wall from the calorifier into a much smaller tank, an ordinary square one, standing on the floor. From the bottom of this yet another pipe tracked right back across the room and up near the boiler itself to a bulbous metal contraption just higher than my head. An electric pump. It finished the circuit by pumping the condensed water up from the tank on the floor and returning it to the boiler, to be boiled, steamed and condensed all over again. Round and round, continuously.
So far, so good. But if you interfered with the circuit so that the water didn’t get back into the boiler, and at the same time kept the heat full on at the bottom, all the water inside the cylinder gradually turned to steam. Steam, which was strong enough to drive a liner, or pull a twelve coach train, but could in this case only get out at all through a narrow, closely spiralled pipe.
This type of boiler, built not for driving an engine but only for heating water, wasn’t constructed to withstand enormous pressures. It was a toss-up, I thought, whether when all the water had gone the fast expanding air and steam found a weak spot to break out of before the flames burnt through the bottom. In either case, the boiler would blow up.
On the outside of the boiler there was a water gauge, a foot-long vertical glass tube held in brackets. The level of water in the tube indicated the level of water in the boiler. Near the top of the gauge a black line showed what the water level ought to be. Two thirds of the way down a broad red line obviously acted as a warning. The water in the gauge was higher than the red line by half an inch.
To put it mildly, I was relieved. The boiler wasn’t bulging. The explosion lay in the future: which gave me more time to work out how to prevent it. As long as it would take Oxon and Kraye to decide on a repeat search, perhaps.
I could simply have turned out the flame, but Kraye and Oxon would notice that the noise had stopped, and merely light it again. Nothing would have been gained. On the other hand, I was sure that the flame was higher than it should have been at night, because the water in the ladies’ tap was nearly boiling.
Gingerly I turned the adjusting wheel on the oil line. Half a turn. A full turn. The roaring seemed just as loud. Another turn: and that time there was a definite change. Half a turn more. It was perceptibly quieter. Slowly I inched the wheel around more, until quite suddenly the roar turned to a murmur. Too far. Hastily I reversed. At the point where the murmur was again a roar, I left it.
I looked consideringly at the square tank of condensed water on the floor. It was this, overflowing, which was making the pool of water; and it was overflowing because the contents were not being pumped back into the boiler. If they’ve broken the pump, I thought despairingly, I’m done. I didn’t know the first thing about electric pumps.
Another sentence from that far away school lesson floated usefully through my mind. For safety’s sake, every boiler must have two sources of water.
I chewed my lower lip, watching the water trickle down the side of the tank on to the floor. Even in the few minutes I had been there the pool had spread. One source of water was obviously knocked out. Where and what was the other?
There were dozens of pipes in the boiler room; not only oil pipes and water pipes, but all the electric cables were installed inside tubes as well. There were about six separate pipes with stop cocks on them. It seemed to me that all the water for the entire building came in through the boiler room.
Two pipes, apparently rising mains, led from the floor up the wall and into the calorifier. Both had stop-cocks, which I tested. Both were safely open. There was no rising main leading direct into the boiler.
By sheer luck I was half way round the huge cylinder looking for an inlet pipe when I saw the lever type door handle move down. I leapt for the only vestige of cover, the space between the boiler and the wall. It was scorching hot there: pretty well unbearable.
Kraye had to raise his voice to make himself heard over the roaring flame.
‘You’re sure it’s still safe?’
‘Yes, I told you, it won’t blow up for three hours yet. At least three hours.’
‘The water’s running out already,’ Kraye objected.
‘There’s a lot in there.’ Oxon’s voice came nearer. I could feel my heart thumping and hear the pulse in my ears. ‘The level’s not down to the caution mark on the gauge yet,’ he said. ‘It won’t blow for a long time after it goes below that.’
‘We’ve got to find Halley,’ Kraye said. ‘Got to.’ If Oxon moved another step he would see me. ‘I’ll work from this end; you start again from the other. Look in every cupboard. The little rat has gone to ground somewhere.’
Oxon didn’t answer audibly. I had a sudden glimpse of his sleeve as he turned, and I shrank back into my hiding place.
Because of the noise of the boiler I couldn’t hear them go away through the door, but eventually I had to risk that they had. The heat where I stood was too appalling. Moving out into the ordinarily hot air in the middle of the room was like diving into a cold bath. And Oxon and Kraye had gone.
I slipped off my jacket and wiped the sweat off my face with my shirt sleeve. Back to the problem: water supply.
The pump looked all right. There were no loose wires, and it had an undisturbed, slightly greasy, slightly dirty appearance. With luck, I thought, they hadn’t damaged the pump, they’d blocked the pipe where it left the tank. I took off my tie and shirt as well, and put them with my jacket on the grimy floor.
The lid of the tank came off easily enough, and the water, when I tested it, proved to be no more than uncomfortably hot. I drank some in my cupped palm. The running and the heat had made me very thirsty, and although I would have preferred it iced, no water could have been purer; or more tasteless, though I was not inclined to be fussy on that point.
I stretched my arm down into the water, kneeling beside the tank. As it was only about two feet deep I could touch the bottom quite easily, and almost at once my searching fingers found and gripped a loose object. I pulled it out.
It was a fine mesh filter, which should no doubt have been in place over the opening of the outlet pipe.
Convinced now that the pipe was blocked from this end, I reached down again into the water. I found the edge of the outlet, and felt carefully into it. I could reach no obstruction. Bending over further, so that my shoulder was half in the water, I put two fingers as far as they would go into the outlet. I could feel nothing solid, but there did seem to be a piece of string. It was difficult to get it between two fingers firmly enough to pull as hard as was necessary, but gradually with a series of little jerks I managed to move the plug backwards into the tank.
It came away finally so suddenly that I nearly overbalanced. There was a burp from the outlet pipe of the tank and on the other side of the room a sharp click from the pump.