mong these wonderful hills of yours
without exhausting their astonishing resources."

Ballard made allowances for scholastic enthusiasm. He had slighted
geology for the more strictly practical studies in his college course.

"Meaning the broken formations?" he asked.

"Meaning the general topsyturvyism of all the formations. Where you
might reasonably expect to find one stratum, you find others perhaps
thousands of years older--or younger--in the geological chronology. I
wonder you haven't galvanised a little enthusiasm over it: you discredit
your alma mater and me when you regard these marvellous hills merely as
convenient buttresses for your wall of masonry. And, by the way, that
reminds me: neither of you two youngsters is responsible for the
foundations of that dam; isn't that the fact?"

"It is," said Bromley, answering for both. Then he added that the
specifications called for bed-rock, which Fitzpatrick, who had worked
under Braithwaite, said had been uncovered and properly benched for the
structure.

"'Bed-rock,'" said the geologist, reflectively. "That is a workman's
term, and is apt to be misleading. The vital question, under such
abnormal conditions as those presenting themselves in your canyon, is,
What kind of rock was it?"

Bromley shook his head. "You can't prove it by me. The foundations were
all in before I came on the job. But from Fitzpatrick's description I
should take it to be the close-grained limestone."

"H'm," said Gardiner. "Dam-building isn't precisely in my line; but I
shouldn't care to trust anything short of the granites in such a
locality as this."

"You've seen something?" queried Ballard.

"Nothing immediately alarming; merely an indication of what might be.
Where the river emerges from your cut-off tunnel below the dam, it has
worn out a deep pit in the old bed, as you know. The bottom of this pit
must, in the nature of things, be far below the foundations of the
masonry. Had you thought of that?"

"I have--more than once or twice," Ballard admitted.

"Very well," continued the Master of the Rocks; "that circumstance
suggests three interrogation points. Query one: How has the diverted
torrent managed to dig such a deep cavity if the true primitives--your
workman's 'bed-rock'--under-lie its channel cutting? Query two: What
causes the curious reverberatory sound like distant thunder made by the
stream as it plunges into this pit--a sound suggesting subterranean
caverns? Quer