d with the spoor of desert
animals that drank the bitter water in extremity. Then it ran straight
to a wide reef of lava. Sandy set down the collie. Grit ran fast across
the pitted surface, ahead of the horses, waiting for them to cross the
lava. They had hard work to get him to come to hand again, but he gave
in at last to the knowledge that they would not go on otherwise.

"Sand's too hot fo' yore pads, dawg," said Sandy, "Raise the mischief
with that tape. Shack erlong, Pronto. Give you a slice of Pedro's
dried-apple pie when we git back, to make up for workin' you Sunday."
The pinto tossed a pink muzzle and his master reached to pat the dusty,
sweat-streaked neck. Alkali rose about them in clouds. Grit's trail,
though blurred in the soft soil, was plain enough. The two riders went
silently on at a steady walking gait. Talk in the saddle with men who
make range-riding a business comes only in spurts.

"Never see a prospector with a dawg afore," said Sam at last. "An' that
a sheep dawg."

"Dawg 'ud be apt to tucker out in desert travel," agreed Sandy. "Mean
one more mouth fo' water."

He, like Sam, speculated on the kind of man P. Casey--if it was Casey
they were after--might be. If not a sheepman or a prospector, a third
probability made him an outlaw, a man with a price on his head, hiding
in the wilds from punishment. It sufficed to them that he was a man whom
a dog loved enough to bear a call to help his master.

Slowly, the mesa ahead took on more definite shape. The shadows resolved
themselves into ravines and canyons. They entered a gorge filled with
boulders and rounded rocks, over which the sure-footed ponies made
clattering, slippery progress. Here and there the gaunt skeleton of a
tree, white as if lime-washed, showed that once cottonwoods had
flourished before the devouring desert had claimed the territory. The
cactus was all prickly pear, the gray-green flesh of the flat leaves
starred with brilliant blossom. Along one side of the canyon, mounting
zigzag, showed the remains of a road, broken down by landslip and the
furious rush of cloud-burst waters.

Making this, finding it free of wagon sign or horse tracks, Sandy picked
up Grit's trail once again. The collie wriggled, shot up its muzzle,
whined, licked Sandy's face.

"Nigh there," suggested Sam. Sandy nodded and let the dog get down. Grit
raced off, nose high, streaking around a curve. When they reached it he
was out of sight. The road had bee