The masons were setting the coping course on the great wall on a day when Gardiner's studious enthusiasm carried him beyond the dinner-hour at Castle 'Cadia and made him an evening guest in the engineer's adobe; and in the after-supper talk it transpired that the a.s.sistant in geology had merely s.n.a.t.c.hed a meagre fortnight out of his work in the summer school, and would be leaving for home in another day or two.

Both of the young men protested their disappointment. They had been too busy to see anything of their guest in a comradely way, and they had been looking forward to the lull in the activities which would follow the opening celebration and promising themselves a more hospitable entertainment of the man who had been both Mentor and elder brother to them in the Boston years.

"You are not regretting it half as keenly as I am," the guest a.s.sured them. "Apart from losing the chance to thresh it out with you two, I have never been on more fascinatingly interesting geological ground. I could spend an entire summer among 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 b.u.t.tresses 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 circ.u.mstance 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? Query three--and this may be set down as the most important of the trio: Why is the detritus washed up out of this singular pot-hole a friable brown shale, quite unlike anything found higher up in the bed of the stream?"

The two young men exchanged swift glances of apprehension. "Your deductions, Professor?" asked Bromley, anxiously.

"Now you are going too fast. True science doesn't deduce: it waits until it can prove. But I might hazard a purely speculative guess. Mr.

Braithwaite's foundation stratum--your contractor's 'bed-rock'--may not be the true primitive; it may in its turn be underbedded by this brown shale that the stream is washing up out of its pot-hole."

"Which brings on more talk," said Ballard, grappling thoughtfully with the new perplexities forming themselves upon Gardiner's guess.

"Decidedly, one would say. Granting my speculative answer to Query Number Three, the Arcadia Company's dam may stand for a thousand years--or it may not. Its life may possibly be determined in a single night, if by any means the water impounded above it should find its way through Fitzpatrick's 'bed-rock' to an underlying softer stratum."

Ballard's eyes were fixed upon a blue-print profile of Elbow Canyon pinned upon the wall, when he said: "If that pot-hole, or some rift similar to it, were above the dam instead of below it, for example?"

"Precisely," said the geologist. "In five minutes after the opening of such an underground channel your dam might be transformed into a makeshift bridge spanning an erosive torrent comparable in fierce and destructive energy, to nothing milder than a suddenly released Niagara."

Silence ensued, and afterward the talk drifted to other fields; was chiefly reminiscent of the younger men's university years. It was while Bromley and Gardiner were carrying the brunt of it that Ballard got up and went out. A few minutes later the out-door stillness of the night was shattered by the sharp crack of a rifle, and other shots followed in quick succession.

Bromley sprang afoot at the first discharge, but before he could reach the door of the adobe, Ballard came in, carrying a hatful of roughly crumbled brown earth. He was a little short of breath, and his eyes were flashing with excitement. Nevertheless, he was cool enough to stop Bromley's question before it could be set in words.

"It was only one of the colonel's Mexican mine guards trying a little rifle practice in the dark," he explained; and before there could be any comment: "I went out to get this, Gardiner"--indicating the hatful of earth. "It's a sample of some stuff I'd like to have you take back to Boston with you for a scientific a.n.a.lysis. I've got just enough of the prospector's blood in me to make me curious about it."

The geologist examined the brown earth critically; pa.s.sed a handful of it through his fingers; smelled it; tasted it.

"How much have you got of this?" he asked, with interest palpably aroused.

"Enough," rejoined the Kentuckian, evasively.

"Then your fortune is made, my son. This 'stuff,' as you call it, is the basis of Colonel Craigmile's millions. I hope your vein isn't a part of his."

Again Ballard evaded the implied question. "What do you know about it, Gardiner? Have you ever seen any of it before?"

"I have, indeed. More than that, I have 'proved up' on it, as your Western miners say of their claims. A few evenings ago we were talking of expert a.n.a.lyses--the colonel and young Wingfield and I--up at the house of luxuries, and the colonel ventured to wager that he could stump me; said he could give me a sample of basic material carrying fabulous values, the very name of which I wouldn't be able to tell him after the most exhaustive laboratory tests. Of course, I had to take him up--if only for the honour of the Inst.i.tute--and the three of us went down to his laboratory. The sample he gave me was some of this brown earth."

"And you a.n.a.lysed it?" inquired Ballard with eagerness unconcealed.

"I did; and won a box of the colonel's high-priced cigars, for which, unhappily, I have no possible use. The sample submitted, like this in your hat, was zirconia; the earth-ore which carries the rare metal zirconium. Don't shame me and your alma mater by saying that this means nothing to you."

"You've got us down," laughed Bromley. "It's only a name to me; the name of one of the theoretical metals cooked up in laboratory experiments.

And I venture to say it is even less than that to Breckenridge."

"It is a very rare metal, and up to within a few years has never been found in a natural state or produced in commercial quant.i.ties,"

explained the a.n.a.lyst, mounting and riding his hobby with apparent zest.

"A refined product of zirconia, the earth itself, has been used to make incandescent gas-mantles; and it was M. Leoffroy, of Paris, who discovered a method of electric-furnace reduction for isolating the metal. It was a great discovery. Zirconium, which is exceedingly dense and practically irreducible by wear, is supplanting iridium for the pointing of gold pens, and its value for that purpose is far in excess of any other known substance."

"But Colonel Craigmiles never ships anything from his mine, so far as any one can see," Ballard cut in.

"No? It isn't necessary. He showed us his reduction-plant--run by water-power from the little dam in the upper canyon. It is quite perfect. You will understand that the actual quant.i.ty of zirconium obtained is almost microscopic; but since it is worth much more than diamonds, weight for weight, the plant needn't be very extensive. And the fortunate miner in this instance is wholly independent of the transportation lines. He can carry his output to market in his vest pocket."

After this, the talk, resolutely shunted by Ballard, veered aside from Arcadian matters. Later on, when Bromley was making up a shake-down bed in the rear room for the guest, the Kentuckian went out on the porch to smoke. It was here that Bromley found him after the Bostonian had been put to bed.

"Now, then, I want to know where you got that sample, Breckenridge?" he demanded, without preface.

Ballard's laugh was quite cheerful.

"I stole it out of one of the colonel's ore bins at the entrance of the mine over yonder."

"I thought so. And the shots?"

"They were fired at me by one of the Mexican night guards, of course.

One of them hit the hat as I was running away, and I was scared stiff for fear Gardiner's sharp old eyes would discover the hole. I'm right glad for one thing, Loudon; and that is that the mine is really a mine.

Sometimes I've been tempted to suspect that it was merely a hole in the ground, designed and maintained purely for the purpose of cinching the Arcadia Company for damages."

Bromley sat up straight and his teeth came together with a little click.

He was remembering the professor's talk about the underlying shales, and a possible breach into them above the dam when he said: "Or to--" but the sentence was left unfinished. Instead, he fell to reproaching Ballard for his foolhardiness.

"Confound you, Breckenridge! you haven't sense enough to stay in the house when it's raining out-of-doors! The idea of your taking such reckless chances on a mere whiff of curiosity! Let me have a pipeful of that tobacco--unless you mean to hog that, too--along with all the other risky things."

XXI

MR. PELHAM'S GAME-BAG