Before leaving the inner end, the two Americans had selected several specimens of the vein-rock from the sides and roof of the tunnel, and other pieces were gathered as they returned. When daylight was reached they spread these specimens out and talked them over, explaining to Sandy, who turned out rather wiser in respect to minerals than he had claimed to be, what were the prominent characteristics of each kind of rock represented.
A few of the fragments, showing some peculiar brown nodules and threads, they separated from the rest, and compared them with similar pieces taken from the overturned car-load on the dump, which had excited their attention before. None of the rock at the entrance had shown this characteristic; all pieces of that kind, they discovered, had come from the innermost depth.
“If we could get past that barrier I think we should find much more of it,” Max remarked.
“We know well enough as to that,” Len replied, “for certainly that car-load was about the last one brought from the mine, and must show what the breast is made of.”
“What do you mean by the breast?” Sandy inquired.
“The rock across the end of the tunnel into which the digging is carried forward.”
“Well,” Max resumed, “the gangue there, judging by the car-load of specimens, contains more of this brown stuff than anything we saw as far as we went, so I think it is fair to conclude that it increases steadily in that direction, and that if the tunnel were pushed farther the whole vein would be seen, before very long, to be well impregnated with it, taking the place of this useless copper and quartz.”
“Can we not examine the outcrop?” Sandy asked, “and learn something from that?”
The outcrop of a vein is that part of it which appears above the surface of the soil, or enclosing rocks,—crops out, as geologists say.
“I don’t know; perhaps so. It would do no harm to go and take a look at it.”