Mitsuitei took the crumbly soil cores as they came, examined them quickly—they were arriving every few seconds—and filed them in numbered compartments in a specimen case he had opened. Detailed stratigraphy would come later. For some time there was no gross evidence of change in the soil; not, in fact, until his first case had been filled.
"Can you stop that thing for a moment, Rob?" he asked at this point. "I don't want to lose track of these, and will have to hold up while I open a new case."
"All right. I thought you'd want to stop for thought soon anyway."
"Why?"
"Because the mole is nearly four meters down, well below the depth at which we hit bedrock before, and is still in soil."
"Eh? But—but it's still ordinary soil; none of your volcanic ash."
"Tuff had been eroded out of a lot of the joints in the cliffs. There's no reason to expect it to be at the same level as the surrounding rock."