There was a place where there was a row of trees along such a water-course. Half the row was fallen, and a part of the rest was tilted. The remainder stood upright and firm. All the vegetation was perfectly familiar. Most colonies have some vegetation, at least, directly descended from the mother-planet Earth. But this island on Canna III had been above-water perhaps no more than three or four thousand years. There had been no time for local vegetation to develop. When the Survey took it over, there was nothing but tidal seaweed, only one variety of which had been able to extend itself in weblike fashion over the soil above water. Terrestrial plants had wiped it out, and everything was green and human-introduced. But there was something wrong with the ground. At this place the top of the soil bulged, and tall corn-plants grew extravagantly in different directions. At another, there was a narrow, lipless gash in the ground's surface. An irrigation-ditch poured water into it. It was not filled. Barnes said: "Excuse me, sir, but how the devil did this happen?" "There's been irrigation," said Bordman patiently. "The soil here was all ocean-bottom, once--it used to be what is called globigerinous ooze. There's no sand, and no stones. There's only bed-rock and formerly abyssal mud. And some of it underneath is no longer former. It's globigerinous ooze again." He waved his hand at the landscape. It had been remarkably tidy, once. Every square foot of ground had been cultivated. The highways were of limited width, and the houses were neat and trim. It was, perhaps, the most completely civilized landscape in the galaxy. Bordman added: "You said the stuff felt like soap. In a way it's acting like soap. It lies on slightly slanting, effectively smooth rock, like a soap-cake on a sheet of metal that's tilted a bit. And that's the trouble. So long as a cake of soap is dry on the bottom it doesn't move. Even if you pour water on top, like rain, the top will wet, and the water will flow off, but the bottom won't wet until all the soap is dissolved away. While that was the process here, everything was all right. But they've been irrigating." They passed a row of neat cottages facing the road. One had collapsed completely. The others looked absolutely normal. The bolster-truck went on. Bordman said, frowning: "They wanted the water to go into the soil, so they arranged it. A little of that did no harm. Plants growing dried it out again. One tree evaporates thousands of gallons a day in a good trade-wind. There were some landslides in the early days, especially when storm-swells pounded the cliffs, but on the whole the ground was more firmly anchored when first cultivated than it had been before the colonists came." "But irrigation? The sea's not fresh, is it?"