Merriwell dashed into the chaparral like a whirlwind and beat about in the bushes trying to discover where the person was who needed help. His hunt was vain. Several times he called aloud, from various parts of the chaparral, but without getting any response.
“This beats the deuce!” he muttered, at last, withdrawing from the bushes and throwing a puzzled look about him into the dark. “What the mischief is going on? It can’t be that I imagined I heard a cry for help. If I didn’t, why can’t I find somebody or something to account for it?”
He was greatly disturbed by his failure to locate the source of that alarm. Finally he gave up, and started to regain the road that led down the slope and in among the mine buildings. Scarcely had he turned, however, when that cry in the night once more smote upon his ears.
He whirled to an about face in a flash. “Where are you?” he called.
The cry was repeated, apparently coming from a mass of shadow, to his left, and farther down the slope. He plunged on into the gloom.
“I’ll find out what’s back of this if it takes a leg,” he declared to himself.
The next moment he stumbled over some obstacle, and fell forward. He threw out his hands instinctively to ease his fall, but they came in contact with nothing more substantial than thin air.
118
He dropped through space—not far, yet far enough to give him quite a jolt when he landed on the hard rocks. After a moment he scrambled to a sitting posture and rubbed his bruised shins.
On every side of him the gloom was thick. He could look up, however, and see an oblong patch of sky, studded with stars.
“Thunder!” he exclaimed ruefully. “There’s an open cut on the slope, and I’ve stumbled into it. That’s what a fellow gets for tracking trouble over ground he doesn’t know anything about. But that cry for help! It certainly gets my goat.”
He had lost his cap in his fall, and he groped around in the dark until he found it. Then, getting to his feet, he made his way to the steep bank and began climbing.
An “open cut” is a gouge in the earth made for purposes of exploration. Usually an “open cut” is dug or blasted out in order to make sure of surface indications of a vein, and sometimes it is made in the hunt for a vein that has been lost.
Yet it made little difference how or what that particular open cut was there. The fact of most importance to Merry was that he had fallen into it.
His bruises were of small consequences; and many a time he had landed from a pole vault with a harder jolt. When a youngster keeps in the pink of physical condition, a hard fall now and then is nothing to worry him.
Presently Frank managed to paw and scramble his way to the top of the steep bank; and there he perched, trying to figure out what in blazes it was that had lured him into the pitfall. He could make nothing of it, and at last turned his attention to the buildings below him.
That was not his first visit to the Ophir mine, by any
119
 means. He was fairly familiar with the location of the different buildings, and he knew that the cyanide plant lay at a considerable distance to the left of the mill. It surprised him, though, to discover that his wanderings across the slope had brought him to a point directly opposite the cyanide tanks.
Cyanide of potassium, it may be explained, is one of the two commercially valuable solvents of gold. This cyanide eats up the gold and holds it in solution. For that reason, the drug is used in treating refuse from a stamp mill. In such refuse—technically known as “tailings”—there is always present a small amount of yellow metal which the quicksilver on the copper plates of the mill fails to “catch.” If it were not for the cyanide, this gold would prove a total loss.
The tailings are thrown into tanks, arranged in rows like a series of giant steps. From a large reservoir, high above the rows of vats, the cyanide solution flows by gravity into all the tanks below—entering at the bottom and percolating through the tailings upward to the top, where it flows off and into the row of tanks next below. The solution takes up the gold as it flows, finally depositing its burden of wealth on zinc shavings in what is called the “zinc box.” From the zinc box the solution drops down another step into a sump tank, and from there, at stated intervals, it is pumped back into the reservoir.
Merriwell was familiar with the cyanide plant at the Ophir mine. He had been showed around by the super, and the work had been explained to him. Consequently he was able to recognize the plant from the open cut the moment his eyes rested on the black bulk of the tanks.
For the present the tanks were out of commission. A cyanide “clean-up” is a long and tedious operation,
120
 and the work pauses for a longer or shorter period while the work is going on.
“I’ll slip down among the tanks and look for Lenning,” Frank murmured. “After I talk with him a while, I’ll return to the hotel and go to bed. If the bullion is locked up in a safe, I guess he won’t have any trouble taking care of it. Funny I didn’t think of that before. The strong box here must be a regular teaser for a cracksman.”
Carefully he gained his feet and descended the rough slope to the tanks. At his left, as he stood by the end of the upper tier of vats, was the laboratory building, where the cyanide expert kept his store of the deadly poison that stole the gold from the tailings, and where he had his assay equipment, his furnaces, crucibles, et cetera. The building was............