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 mining and engineering, and the fame of our two friends had been rapidly spreading.

Both scrupulously honest in all things, Reade and Hazelton had also won a reputation as “square” mining men.  With their skill and honesty established, the opinions of the two partners on mining problems were generally respected wherever they happened to be known.

So, in time, Luis Montez had heard of them, and had decided that he needed their services at El Sombrero (The Hat) Mine in the Mexican state of Bonista.  After some correspondence the two engineers had been speedily engaged, and the opening of this volume deals with the time of their arrival at the handsome country house of Senor Montez.

After his host had gone inside, and Harry Hazelton slept on, Tom, who had risen—­to bow to Senor Montez, remained on his feet, pacing slowly and thoughtfully up and down the porch.

“Now that I’ve seen my new employer,” mused Tom, under his breath, “I wonder just how much I really like him.  He’s a polished man, and a charming fellow from the little that I’ve seen of him.  But his talk of ruling these hills, even in life and death—­does that speak well for him.  Is he a knave, or only a harmless braggart?  Is he a man against whom one should be seriously on his guard?  Don Luis’s manners, in general, I admire, but I don’t quite like the cruel expression about his month when he laughs.  However, that may be the way of the country, and I may be the victim of prejudice.  Anyway, as far as Harry and I are concerned, we needn’t worry much about the kind of man Don Luis is.  The few thousands of dollars that he will owe us as his engineers we are pretty certain to get, for Don Luis is a very wealthy man, and he couldn’t afford to cheat us.  For the rest, all he wants us to do is to work hard as engineers and show him how to get more valuable ore out of his mines.  So, no matter what kind of man Don Luis may be, we have nothing to fear from him—­not even being cheated out of our pay.”