 What main motivation did Antler Park have to leave the lens in the barracks?
What with red-spot fever, talking cockatoos and flagpole trees, I was running in circles—especially since Grannie became twins every now and then. We had left the offices of Interstellar Voice three days ago, Earth time, and now as the immense disc of Jupiter flamed across the sky, entered the outer limits of the Baldric. Everything else was blanketed by the sand and the powerful wind that blew from all quarters. If my calculations are right, we've hit it at its narrowest spot." He could be excused this time, however, for this was only our third day on Jupiter's Eighth Moon, and the country was still strange to us. If you haven't read her books, you've missed something. Blood-and-thunder as these books are, however, they have one redeeming feature—authenticity of background. Grannie Annie was the original research digger-upper, and when she laid the setting of a yarn on a star of the sixth magnitude, only a transportation-velocity of less than light could prevent her from visiting her "stage" in person. He was an old prospector Grannie had met, and he had become so attached to the authoress he now followed her wherever she went. As for Xartal, he was a Martian and was slated to do the illustrations for Grannie's new book. And then I was shaking hands with Antlers Park, the manager of I. V. himself. Antlers Park flicked the ash from his cheroot and shrugged. It's no use to the people of Earth but of untold value on Mars. Then it was found that this ore, Acoustix, revitalized their sounding apparatus, and the rush was on." "But up until now this moon is the only place where it can be found. "There are two principal forms of life in the Baldric; flagpole trees and a species of ornithoid resembling cockatoos. And when Antlers Park stuttered evasively, the old lady snorted, "Fiddlesticks, I never saw trouble yet that couldn't be explained. So now here we were at the outer reaches of the Baldric, four travelers on foot with only the barest necessities in the way of equipment and supplies. Xartal, the Martian illustrator, already had a notebook in his hands and was sketching a likeness of the creature. Above us, the great disc of Jupiter began to descend toward the horizon. And then all at once Grannie stopped again, this time at the top of a high ridge. Behind her strode a grizzled Earth man in a flop-brimmed hat, another Earth man, and a Martian.
 He knew the value of this spot for Acoustix, and wanted to run the Jimmy Baker out.
 He didn't fully understand the effects of the infra-red rays and wanted to see what it was capable of.  He knew the value of this spot for Acoustix, and wanted to run the Jimmy Baker out.  He was afraid of Grannie Annie discovering his plot and tried to get rid of her.  He had struck a large load of Acoustix and wanted to hide the evidence.