The Doctor was an advocate of leisurely eating, but he impatiently hurried the boys through their breakfast the next morning and set them at work upon the bank with picks and shovels. He explained to them as he had before explained to Tom, that "outcrop" coal—that is to say, the edge of a coal seam exposed by any circumstance and left long exposed, deteriorates in quality and value.
"All the combustible parts of this exposed coal have been evaporated," he said, "until now the stuff is worth scarcely more than so much shale. But unless my knowledge of geology fails me, there lies behind this stuff, some of the very richest coal in Virginia. Our task is to dig in here and find out whether we have here a valuable coal mine or nothing at all."
"Suppose it is the kind of coal you think, Doctor," said Jack, "what is such a mine worth?"
"Nothing and everything. It all depends upon circumstances. A year or two ago the finest coal deposit in the world, located where this is would have been worth no more than the detritus from the hill that is piled up all around here. Such a mine at this place now, is incalculably valuable."
"But what makes so vast a difference?" asked Ed.
"The railroad," answered the Doctor. "A year ago this coal would have been worthless, simply because there was no market for it anywhere within reach. Now the railroad brings the market to the mouth of the mine, as it were. But come, let's get to work. If you want me to talk about King Coal, I'll do it to-night after supper. Just now we must dig for his majesty." Then he grabbed a pick and broke out again singing—
"Old King Coal
Was a jolly old soul," etc.
The boys dug with a will and by nightfall they had dug away three or four feet of the face of the cliff. Every now and then the Doctor would take a bit of the exposed coal and examine it critically under a strong magnifying glass. Every time he did so, he broke out again into the song about "Old King Coal." The boys had never seen him so jubilant.
When they quitted the work and began to prepare supper, the Doctor went into the shaft they had started, broke out a bushel or two of the deepest coal yet reached, and placed it on the fire. He watched it intently as it burned, and just as supper was ready he said:
"We've got it, boys, and no mistake. This is a great mine of the very best coal in the world for making gas, steam and coke, and as these hills are full of iron ore, the mine is precisely where it ought to be. When we dig a little further into that bank we shall come to coal that can be shovelled into a furnace with iron ore on top of it, and used to smelt iron without the trouble or expense of coking. Or we can make as good coke of it as there is in the world, and the vein is eight or nine feet thick, which means a lot, and it has a perfect rock roof, which means a lot more, and the volcanic upheaval which shoved it up here has kindly so placed it that it trends upward, so that in mining it we shall not have to do any pumping. All we've got to do is to dig trenches on each side of our coal car tracks and let the water run out by force of gravitation. I tell you boys, we've discovered the most valuable coal mine in all this region, and as if to make matters still better, it lies just high enough up the mountain to enable us to chute its product down to the railroad without any expense whatever for hauling."