Colorado River, popularly supposed to be the hottest place in
America. The boys, glad that their long journey had come to an end,
felt that it was living up to its reputation as they alighted and
stood in the blistering heat while their personal baggage was thrown
off.

The professor, however, was quite oblivious to the scorching rays of
the afternoon sun. He darted about seeking specimens, and he had soon
gathered up quite a collection of small rocks. In the meantime Zeb
Cummings, who was quite in his element, had helped the boys get their
things together and see them loaded on a mule wagon which rattled them
off to a small hotel, for they did not want to make themselves any
more conspicuous than was necessary.

The boys wore gray flannel shirts, khaki trousers, stout high boots
and broad-brimmed hats, and had fastened red handkerchiefs round their
throats to keep off the sun from the back of their necks. Zeb had a
similar outfit.

The professor, however, still wore his baggy black garments, his only
concession to the heat being a big green umbrella, which looked like a
gigantic verdant mushroom. As they drove off in a rickety sort of bus,
having with difficulty persuaded the professor to leave off specimen
hunting for a while, the boys did not notice that from the opposite
side of the train three young men had alighted who, from a point of
vantage behind a water tower, watched their movements.

The trio were Bill Masterson and his two cronies, Sam Higgins and Eph
Compton.

"Well, here we are, Eph," said Bill, as they watched the boys drive
off.

"Yes, and here they are, too," grunted Eph.

"I'm glad we've got here at last, though. Keeping out of sight on
that train was beginning to get on my nerves."

"Same here," said Sam Higgins, stretching himself. "But I guess we
succeeded in keeping ourselves hidden all right."

"Sure," rejoined Masterson. "They haven't a notion we are here."

In the meantime the lads found accommodations till the next day at the
small hotel on a back street where Zeb had insisted on their coming so
as to escape observation. Yuma is full of prospectors and miners, and
every stranger in town is suspected of having some sort of a scheme,
he explained, and as a consequence is closely watched.

Zeb's first care, therefore, was to circulate a story that the
professor, a noted savant and geologist, was going into the desert
with his party to collect specimens. This appeared to satisfy the