"Those boats yonder?"
Hardwick indicated a boat from which something like a wire basket splashed into the water as he gestured.
"A garden boat, sir," said Barnes. "On this side of the island the sea bottom slopes so gradually, sir, that there are sea gardens on the bottom. Shellfish from Earth do not thrive, sir, but there are edible sea plants. The gardeners cultivate them as on land, sir."
Hardwick reached overside and carefully took his twentieth sample of the sea water. He squinted, and estimated the distance to shore.
"I shall try to imagine someone wearing a diving mask and using a hoe," he said dryly. "What's the depth here?"
"We're half a mile out, sir," said Barnes promptly. "It should be about sixty feet, sir. The bottom seems to have about a three per cent grade, sir. That's the angle of repose of the mud. There's no sand to make a steeper slope possible."
"Three per cent's not bad!"
Hardwick looked pleased. He picked up one of his earlier samples and tilted it, checking the angle at which the sediment came to rest. The bottom mud, here, was essentially the same as the soil of the land. But the soil of the island was infinitely finely-divided. In fresh water it floated practically like a colloid. In sea water, obviously, it sank because of the salinity which made suspension difficult.
"You see the point, eh?" he asked. When Barnes shook his head, Hardwick explained, "Probably for my sins I've had a good deal to do with swamp planets. The mud of a salt swamp is quite different from a fresh-water swamp. The essential trouble with the people ashore is that by their irrigation they've contrived an island-wide swamp which happens to be upside down—the mud at the bottom. So the question is, can it acquire the properties of a salt swamp instead of a fresh-water swamp without killing all the vegetation on the surface? That's why I'm after these samples. As we go inshore the water should be fresher—on a shallowing shore like this with drainage in this direction."
He gestured to the Survey private at the stern of the boat.