"Very well. We're stopping near the middle of the valley one hundred yards from the front. I am getting out, and will walk as close as I can with a sampler and a radiometer. I assume that the radio equipment will continue to relay my suit broadcast back to you." Zaino cringed a little, certain as he was that the tractor's electronic apparatus was in perfect order. It struck him that Dr. Burkett was being more snappish than usual. It never crossed his mind that the woman might be afraid. "Ren, don't get any closer with the tractor unless I call. I'll get a set of temperature readings as soon as I'm close enough. Then I'll try to get a sample. Then I'll come back with that to the tractor, leave it and the radiometer and get the markers to set out." "Couldn't I be putting out the markers while you get the sample, Doctor?" "You could, but I'd rather you stayed at the wheel." Hargedon made no answer, and Burkett resumed her description for the record. "I'm walking toward the front, a good deal faster than it's flowing toward me. I am now about twenty yards away, and am going to take a set of radiation-temperature measures." A brief pause. "Readings coming. Nine sixty. Nine eighty. Nine ninety--that's from the bottom edge near the spine that's being surrounded. Nine eighty-five--" The voice droned on until about two dozen readings had been taped. Then, "I'm going closer now. The sampler is just a ladle on a twelve-foot handle we improvised, so I'll have to get that close. The stuff is moving slowly; there should be no trouble. I'm in reach now. The lava is very liquid; there's no trouble getting the sampler in--or out again--it's not very dense, either. I'm heading back toward the tractor now. No, Ren, don't come to meet me." There was a minute of silence, while Zaino pictured the spacesuited figure with its awkwardly long burden, walking away from the creeping menace to the relative safety of the tractor. "It's frozen solid already; we needn't worry about spilling. The temperature is about--five eighty. Give me the markers, please." Another pause, shorter this time. Zaino wondered how much of that could be laid to a faster walk without the ladle and how much to the lessening distance between flow and tractor. "I'm tossing the first marker close to the edge--it's landed less than a foot from the lava. They're all on a light cord at ten-foot intervals; I'm paying out the cord as I go back to the tractor. Now we'll stand by and time the arrival at each marker as well as we can." "How close are you to the main cone?" asked Zaino. "Not close enough to see its base, I'm afraid. Or to get a sample of it, which is worse. We--goodness, what was that?" Zaino had just time to ask, "What was what?" when he found out. IV