sun-down."
"I'll likely see him then. I won't be loaded for another week and ahalf. Can't you get in touch with him by radio?"
"He isn't carrying one. Most of the prospectors don't. They claim that aradio that won't carry beyond the horizon isn't any good, and one thatwill bounce messages from Earth takes up too much room."
"Well, if I don't see him, you let him know about the chromium."
"Anything to help another Welshman, is that the idea?"
"Well, protection it is that a poor Welshman needs from all the Englishand Scots. Speaking of which--"
"Oh, of course," McIlroy grinned as he refilled the glasses.
"_Slainte, McIlroy, bach._" [Health, McIlroy, man.]
"_Slainte mhor, bach._" [Great Health, man.]
* * * * *
The sun was halfway to the horizon, and Earth was a crescent in the skywhen Evans had quarried all the ice that was available in the cave. Thethought grew on him as he worked that this couldn't be the only suchcave in the area. There must be several more bubbles in the lava flow.
Part of his reasoning proved correct. That is, he found that bychipping, he could locate small bubbles up to an inch in diameter, eachone with its droplet of water. The average was about one per cent of thevolume of each bubble filled with ice.
A quarter of a mile from the tractor, Evans found a promising lookingmound of lava. It was rounded on top, and it could easily be the dome ofa bubble. Suddenly, Evans noticed that the gauge on the oxygen tank ofhis suit was reading dangerously near empty. He turned back to histractor, moving as slowly as he felt safe in doing. Running would use upoxygen too fast. He was halfway there when the pressure warning lightwent on, and the signal sounded inside his helmet. He turned on histen-minute reserve supply, and made it to the tractor with about fiveminutes left. The air purifying apparatus in the suit was not asefficient as the one in the tractor; it wasted oxygen. By using the suitso much, Evans had already shortened his life by several days. Heresolved not to leave the tractor again, and reluctantly abandoned hisplan to search for a large bubble.
* * * * *
The sun stood at half its diameter above the horizon. The shadows of themountains stretched out to touch the shadows of the other mountains. Thedawning line of light covered half of Earth, and Earth turned beneathit.
Cowalczk itched under his suit, and the sweat on his face prickledmaddeningly because he couldn't reach it through his helmet. He pushedhis forehead against the faceplate of his helmet and rubbed off some ofthe sweat. It didn't help much, and it left a blurred spot in hisvision. That annoyed him.
"Is everyone clear of the outlet?" he asked.
"All clear," he heard Cade report through the intercom.
"How come we have to blow the boilers now?" asked Lehman.
"Because I say so," Cowalczk shouted, surprised at his outburst andashamed of it. "Boiler scale," he continued, much calmer. "We've got toclean out the boilers once a year to make sure the tubes in the reactordon't clog up." He squinted through his dark visor at the reactorbuilding, a gray concrete structure a quarter of a mile distant. "Itwould be pretty bad if they clogged up some night."
"Pressure's ten and a half pounds," said Cade.
"Right, let her go," said Cowalczk.
Cade threw a switch. In the reactor building, a relay closed. A motorstarted turning, and the worm gear on the motor opened a valve on theboiler. A stream of muddy water gushed into a closed vat. When the vatwas about half full, the water began to run nearly clear. An electriceye noted that fact and a light in front of Cade turned on. Cade threwthe switch back the other way, and the relay in the reactor buildingopened. The motor turned and the gears started to close the valve. But afragment of boiler scale held the valve open.
"Valve's stuck," said Cade.
"Open it and close it again," said Cowalczk. The sweat on his foreheadstarted to run into his eyes. He banged his hand on his faceplate in anunconscious attempt to wipe it off. He cursed silently, and wiped it offon the inside of his helmet again. This time, two drops ran down theinside of his faceplate.
"Still don't work," said Cade.
"Keep trying," Cowalczk ordered. "Lehman, get a Geiger counter and comewith me, we've got to fix this thing."
Lehman and Cowalczk, who were already suited up started across to thereactor building. Cade, who was in the pressurized control room withouta suit on, kept working the switch back and forth. There was light thatindicated when the valve was open. It was on, and it stayed on, nomatter what Cade did.
"The vat pressure's too high," Cade said.
"Let me know when it reaches six pounds," Cowalczk requested. "Becauseit'll probably blow at seven."
The vat was a light plastic container used only to decant sludge out ofthe water. It neither needed nor had much strength.
"Six now," said Cade.
Cowalczk and Lehman stopped halfway to the reactor. The vat bulged andruptured. A stream of mud gushed out and boiled dry on the face of theMoon. Cowalczk and Lehman rushed forward again.
They could see the trickle of water from the discharge pipe. The motorturned the valve back and forth in response to Cade's signals.
* * * * *
"What's going on out there?" demanded McIlroy on the intercom.
"Scale stuck in the valve," Cowalczk answered.
"Are the reactors off?"
"Yes. Vat blew. Shut up! Let me work, Mac!"
"Sorry," McIlroy said, realizing that this was no time for officials."Let me know when it's fixed."
"Geiger's off scale," Lehman said.
"We're probably O.K. in these suits for an hour," Cowalczk answered. "Isthere a manual shut-off?"
"Not that I know of," Lehman answered. "What about it, Cade?"
"I don't think so," Cade said. "I'll get on the blower and rouse out anengineer."
"O.K., but keep working that switch."
"I checked the line as far as it's safe," said Lehman. "No valve."
* * * * *
"O.K.," Cowalczk said. "Listen, Cade, are the injectors still on?"
"Yeah. There's still enough heat in these reactors to do some damage.I'll cut 'em in about fifteen minutes."
"I've found the trouble," Lehman said. "The worm gear's loose on itsshaft. It's slipping every time the valve closes. There's not enoughpower in it to crush the scale."
"Right," Cowalczk said. "Cade, open the valve wide. Lehman, hand me thatpipe wrench!"
Cowalczk hit the shaft with the back of the pipe wrench, and it broke atthe motor bearing.
Cowalczk and Lehman fitted the pipe wrench to the gear on the valve, andturned it.
"Is the light off?" Cowalczk asked.
"No," Cade answered.
"Water's stopped. Give us some pressure, we'll see if it holds."
"Twenty pounds," Cade answered after a couple of minutes.
"Take her up to ... no, wait, it's still leaking," Cowalczk said. "Holdit there, we'll open the valve again."
"O.K.," said Cade. "An engineer here says there's no manual cutoff."
"Like Hell," said Lehman.
Cowalczk and Lehman opened the valve again. Water spurted out, anddwindled as they closed the valve.
"What did you do?" asked Cade. "The light went out and came on again."
"Check that circuit and see if it works," Cowalczk instructed.
There was a pause.
"It's O.K.," Cade said.
Cowalczk and Lehman opened and closed the valve again.
"Light is off now," Cade said.
"Good," said Cowalczk, "take the pressure up all the way, and we'll seewhat happens."
"Eight hundred pounds," Cade said, after a short wait.
"Good enough," Cowalczk said. "Tell that engineer to hold up a while, hecan fix this thing as soon as he gets parts. Come on, Lehman, let's getout of here."
"Well, I'm glad that's over," said
Cade. "You guys had me worried for awhile."
"Think we weren't worried?" Lehman asked. "And it's not over."
"What?" Cade asked. "Oh, you mean the valve servo you two bashed up?"
"No," said Lehman, "I mean the two thousand gallons of water that welost."
"Two thousand?" Cade asked. "We only had seven hundred gallons reserve.How come we can operate