Their first experiences are told in the opening volume of this
series, "_The Young Engineers In Colorado_." Joining a western
engineering force as "cub" engineers, at first the laughing-stock
of the older engineers on the staff of a new railroad then building
in Colorado, the two boys did their best to make good. How well
they succeeded is known to readers of that volume. Their adventures
in the Rocky Mountains were truly astounding; some of them, especially
those with "Bad Pete," a braggart and scoundrel of the old school,
were sometimes mirth-provoking and sometimes tragic. Other adventures
were vastly more serious. When the boys reached the crisis of
their work it seemed as though every tree in the mountains concealed
an enemy. All these and many more details are told in that first
volume.

In "_The Young Engineers In Arizona_," we found the pair engaged
in a wholly new task--that of filling up an apparently unfillable
quicksand in the desert so that a railway roadbed might be built
safely over the dangerous quicksand that had justly earned the
name of the "Man-killer." Here, too, adventures quickly appeared
and multiplied, until even the fearful quicksand became a matter
of smaller importance to the chums. How the two young engineers
persevered and fought pluckily all the human and other obstacles
to their success the readers of the second volume now know fully.

Then Tom and Harry, who had been putting in many spare hours,
days and weeks on the study of metallurgy and the assaying of
precious metals, went, for a "vacation," to Nevada, there further
to pursue their studies. Quite naturally they became interested
in gold mining itself, and all their adventures, their mishaps,
failures, fights and final successes were fully chronicled in
the third volume, entitled "_The Young Engineers in Nevada_." The
mine that finally proved a dividend payer was named "The Ambition
Mine." A staunch Nevadan, Jim Ferrers, by name, became their
partner in the Ambition. Jim, who was an old hand at Nevada mining,
was now managing the mine while Tom and Harry, after going East
and establishing an engineers' office in a large city not far
from New York, had traveled to other states, studying mines and
assay methods. Within the last few months, so rapid had been
their progress in mine engineering, that they had been consulted
by a number of mine owners. Articles that they had written had
appeared in journals devoted to