He stopped. Frank skated on ahead, noticed presently that Jim was not following him and came back. "What's up?" he called out.

"I thnk this is it."

"Hmm... could be." They removed their skates and climbed the ramp. At the top, set back a short distance from the bank, was one of the bubble-shaped buildings which are the sign anywhere on Mars of the alien from Earth. Beyond it a foundation had been started for the reducing plant. Jim heaved a big sigh. Frank nodded and said, "Just about where we expected to find it."

"And none too soon," added Jim. The Sun was close to the western horizon and dropping closer as they watched.

There was, of course, no one in the shelter; no further work would be done at this latitude until the following spring. The shelter was unpressurized; they simply unlatched the outer door, walked through the inner door without delay. Frank groped for the light switch, found it, and lighted up the place -the lighting circuit was powered by the building's atomicfuel power pack and did not require the presence of men.

It was a simple shelter, lined with bunks except for the space occupied by the kitchen unit. Frank looked around happily. "Looks like we've found a home from home, Jim."

"Yep." Jim looked around, located the shelter's thermostat, and cut it in. Shortly the room became warmer and with it there was a soft sighing sound as the building's pressure regulator, hooked in with the thermostat, started the building's supercharger, hi a few minutes the boys were able to remove their masks and finally their outdoors suits as well.

Jim poked around the kitchen unit, opening cupboards and peering into shelves. "Find anything?" asked Frank.

"Nary a thing. Seems like they could have left at least a can of beans."

"Now maybe you're glad I raided the kitchen before we left. Supper in five minutes."

"Okay, so you've got a real talent for crime," acknowledged Jim. "I salute you." He tried the water tap. "Plenty of water in the tanks," he announced.

"Good!" Frank answered. "That saves me having to go down and chip ice. I need to fill my mask. I was dry the last few miles." The high coxcomb structure on a Mars mask is not only a little supercharger with its power pack, needed to pressurize the mask; it is also a small water reservoir. A nipple in the mask permits me wearer to take a drink outdoors, but this is a secondary function. The prime need for water in a Mars mask is to wet a wick through which the air is forced before it reaches the wearer's nose.

"You were? Well, for crying out loud-don't you know better than to drink yourself dry?"

"I forgot to fill it before we left."

"Tourist!"

"Well, we left in kind of a hurry, you know."

"How long were you dry?"

"I don't know exactly," Frank evaded.

"How's your throat?"

"All right. A little dry, maybe."

"Let me see it," Jim persisted, coming closer.

Frank pushed him away. "I tell you it's all right. Let's eat."

"Well-okay."

They dined off canned corned beef hash and went promptly to bed. Willis snuggled up against Jim's stomach and imitated his snores.

Breakfast was more of the same, since there was some hash left and Frank insisted that they not waste anything. Willis had no breakfast since he had eaten only two weeks before, but he absorbed nearly a quart of water. As they were about to leave Jim held up a flashlight. "Look what I found."

"Well, put it back and let's go."

"I think I'll keep it," Jim answered, stuffing it in his bag. "We might have a use for it."

"We won't and it's not yours."

"For criminy's sake, I'm not swiping it; I'm just borrowing it. This is an emergency."

Frank shrugged. "Okay, let's get moving." A few minutes later they were on the ice and again headed south. It was a beautiful day, as Martian days almost always are; when the Sun was high enough to fill the slot of die canal it was almost balmy, despite the late season. Frank spotted the tell-tale hoisting beam of a Project shelter around midday and they were able to lunch inside, which saved them the tedious, messy, and unsatisfactory chore of trying to eat through the mouth valve of a respirator mask. The shelter was a twin of the first but no foundation for the plant had as yet been built near it.

As they were preparing to leave the shelter Jim said, "You look sort of flushed, Frank. Got a fever?"

"That's just the bloom of health," Frank insisted. "I'm fine." Nevertheless he coughed as he put on his mask. "Mars throat," Jim thought but said nothing as there was nothing that he could do for Frank.

Mars throat is not a disease in itself; it is simply an extremely dry condition of the nose and throat which arises from direct exposure to Martian air. The humidity on Mars is usually effectively zero; a throat dehydrated by it is wide open to whatever disease organisms there may be present in the human throat at the time. The result is usually a virulent sore throat.

The afternoon passed without incident. As the Sun began to drop toward the skyline it seemed possible that home was not much more than five hundred miles away. Jim had watched Frank closely all afternoon. His chum seemed to be skating as strongly as ever; perhaps, he decided, the cough was just a false alarm. He skated up alongside Frank. "I guess we had better start watching for a shelter."

"Suits me."

Soon they passed another of the ramps built by long-dead Martians, but there was no hoisting beam above it nor any other sign of terrestrial activity. The banks, though somewhat lower now, were still too high to see over. Jim stepped up the stroke a bit; they hurried on.

They came to another ramp, but again there was nothing to suggest that a shelter might be above it. Jim stopped. "I vote we take a look up on the bank," he said. "We know they build the shelters by the ramps and they may have taken the hoist down for some reason."

"It would just be wasting valuable time," Frank protested. "If we hurry, we can get to another ramp before dark."

"Well, if you say so-" Jim shoved off and picked up speed.

The next ramp was the same story; Jim stopped again. "Let's take a look," he pleaded. "We can't possibly reach the next one before sundown."

"Okay." Frank stopped over and tugged at his skates.

They hurried up the bank and reached the top. The slanting rays of the Sun showed nothing but the vegetation bordering the canal.

Jim felt ready to bawl through sheer weariness and disappointment. "Well, what do we do now?" he said.

"We go back down," Frank answered, "and keep going until we find it."

"I don't think we could spot one of those hoist beams in the dark."

"Then we keep going," Frank said grimly, "until we fall flat on our faces."

"More likely we'll freeze."

"Well, if you want my opinion," Frank replied, "I think we're washed up. I, for one, can't keep going all night, even if we don't freeze."

"You don't feel good?"

"That's putting it mildly. Come on."

"All right."

Willis had climbed out of the bag and up on Jim's shoulder, in order to see better. Now he bounced to the ground and rolled away. Jim snatched at him and missed. "Hey! Willis! Come back here!"

Willis did not answer. Jim started after him. His progress was difficult. Ordinarily he would have gone under the canal plants, but, late in the day as it was, most of them had lowered almost to knee height preparatory to withdrawing into the ground for the night. Some of the less hardy plants were already out of sight, leaving bare patches of ground.

The vegetation did not seem to slow up Willis but Jim found it troublesome; he could not catch the little scamp. Frank shouted, "'Ware water-seekers! Watch where you put your feet!" Thus warned, Jim proceeded more carefully-and still more slowly. He stopped. "Willis! Oh, Willis! Come back! Come back, dawggone it, or we'll go away and leave you." It was a completely empty threat.