He explained to Birt that in certain formations, however, gold is
associated with iron pyrites, and when the mineral is properly
roasted, this process serving to expel the sulphur, the fine
particles of gold are found held in the resulting oxide of iron.
But the variety of the mineral discovered down the ravine he said
was valueless, unless occurring in vast quantities, when it is
sometimes utilized in the production of sulphur.

"I wonder," Birt broke out suddenly, "if the assayer won't find no
gold in them samples ez Nate sent him."

The professor laughed. "The assayer will need the 'philosopher's
stone' to find gold in any samples from this locality."

"Ye knowed then, all the time, ez this stuff warn't gold?" asked
Birt.

"All the time," rejoined the elder.

"An' Nate hev got the steepest, rockiest spot in the kentry ter pay
taxes on," resumed Birt, reflectively. "An' he hev shelled out a
power o' money ter the surveyor, an' sech, a'ready. I reckon he'll
be mightily outed when he finds out ez the min'ral ain't gold."

Birt stopped short in renewed anxiety.

That missing grant! Somehow he felt sure that Nate, balked of the
great gains he had promised himself, would wreak his disappointment
wherever he might; and since the land was of so little value, he
would not continue to deny himself his revenge for fear that an