hispered Dave.

A black, undulating line wound out of the cedars, a line of horses
approaching with drooping heads, hurrying a little as they neared the
spring.

"Twenty-odd, all blacks and bays," said August, "and some of them are
mustangs. But where's Silvermane?--hark!"

Out among the cedars rose the peculiar halting thump of a hobbled horse
trying to cover ground, followed by snorts and crashings of brush and
the pound of plunging hoofs. The long black line stopped short and began
to stamp. Then into the starlit glade below moved two shadows, the first
a great gray horse with snowy mane; the second, a small, shiny, black
mustang.

"Silvermane and Bolly!" exclaimed August, "and now she's broken her
hobbles."

The stallion, in the fulfilment of a conquest such as had made him
king of the wild ranges, was magnificent in action. Wheeling about her,
neighing, and plunging, he arched his splendid neck and pushed his
head against her. His action was that of a master. Suddenly Black Bolly
snorted and whirled down the glade. Silvermane whistled one blast of
anger or terror and thundered after her. They vanished in the gloom of
the cedars, and the band of frightened horses and mustangs clattered
after them.

"It's one on me," remarked Billy. "That little mare played us at the
finish. Caught when she was a yearling, broken better than any mustang
we ever had, she has helped us run down many a stallion, and now she
runs off with that big white-maned brute!"

"They'll make a team, and if they get out of here we'll have to chase
them to the Great Salt Basin," replied Dave.

"Mescal, that's a well-behaved mustang of yours," said August; "not only
did she break loose, but she whistled an alarm to Silvermane and his
band. Well, roll in now, everybody, and sleep."

At breakfast the following day the Naabs fell into a discussion upon the
possibility of there being other means of exit from the plateau than
the two trails already closed. They had never run any mustangs on the
plateau, and in the case of a wild horse like Silvermane, who would take
desperate chances, it was advisable to know the ground exactly. Billy
and Dave taking their mounts from the sheep-corral, where they had put
them up for the night, rode in opposite directions around the rim of
the plateau. It was triangular in shape, and some six or seven miles in
circumference; and the brothers rode around it in less than an hour.

"Corralled," said Dave, laconic