Bevens dismounted and began walking around the mining area, evidently arguing with himself and doing complex calculations in his head, much as he had on the summit a few hours earlier. He poked around in a few of the coal piles, compared several samples, asked questions whenever he encountered a worker, and nearly nose- dived into one of the processing bins trying to get a closer look at the floating chunks. Frank and Cameron were impressed at the scrutiny with which he scoured the facilities; the miners saw matters differently. This new, intrusive busy-body was just another nuisance they would learn to avoid.
When he had completed his preliminary inspections, Bevens walked over to the other two and said, "All right, let's take a look at your coal mine."
Frank left for a moment and returned with three cast iron mining helmets. "No one is allowed past the entrance without a helmet. Put them on; we can dispense with the lamps his time. There should be enough light inside from the section working on the active coal face."
Cameron and Bevens duplicated Frank's example, donning the heavy caps and fastening the chin straps, then followed him to the mine entrance. It was an opening into the mountain side about fifteen feet wide by eight feet high, framed on three sides by thick wooden beams. As they were about to enter, a miner leading a horse drawn wagon filled with newly extracted coal emerged from the dark tunnel. Bevens studied the load as they stepped aside, allowing the miner to pass. He was surprised: it was almost all pure coal, with very little aggregate. In his judgment, they must be mining an exceptionally rich seam.
Frank entered first and waved on the others to stay close. They had made good progress during the past six months, reaching a depth of forty feet into the interior. Support timbers, on the ribs and ceiling, had been raised every four feet. Strings of oil burning davy lamps were looped from timber to timber, on both ribs and overburden, as far as the mine entry extended. Although the tunnel had seemed shrouded in darkness from outside the portal, it was surprisingly easy to see while inside once a person's pupils adjusted to a dimmer but more concentrated light,
They walked along slowly, giving Bevens enough time to inspect everything that caught his eye, and reached the end of the excavated tunnel, the working face of the mine, in five minutes. A section of four men and an assistant foreman, wearing davy lamps affixed to their helmets, were working the face, knocking down loosened chunks of coal with their tools and shoveling the yield into a waiting wagon. The foreman nodded at Frank but did not otherwise alter the rhythm of his work; the workers in his section, for their own part, took no notice of the three visitors.
Bevens knelt down and examined a slab of the coal face still untouched. It was as uncontaminated as the load in the wagon. If Frank could find a better way to transport his loads to Morgantown, he would soon become a rich man. It was unlikely that his competitors could market coal of comparable quality. He glanced up at Frank and rose with a barely perceptible nod of his head. He was done; they could leave. He had seen everything he needed to see.
The three men did not speak again until they emerged from the mine. After returning the helmets to a wooden bin reserved for mining equipment, they remounted and rode toward the tent encampment spread along the grassy plateau. A wood frame building was being erected at the end of one row of tents; it would provide permanent housing for a miner and his family; according to Frank, it was only the first of many to come.
Once the horses were tethered and everyone seated on canvas folding chairs around an open fire pit, Frank passed out fresh mugs of coffee and waited; but Cameron and Bevens remained silent, preferring that he ask the questions.
Finally, Frank began, "Well?"
"Your entryway is beginning to slant downward as the face moves further inby," Bevens remarked, not in a critical way, but he clearly wanted an explanation.
"Yes. In the beginning, we tried to keep the floor as level as possible, but the seam kept moving down an incline, so we followed."
"I see. The best thing to do under the circumstances, no doubt"
"Where should we go next," Frank asked, skipping ahead to the question he most needed answered.
"Well, what you've accomplished so far is commendable. The tunnel has adequate lighting, and the walls and ceiling are well shored up. Your workers seem to know their jobs. But you have serious problems, lots of them."
"I'm listening. By the way, do you think we should begin digging again on the summit?"
"No, absolutely not. In my opinion, your mountain is probably crammed full of coal, but it's scattered everywhere, from the top down to the base of the wall. I doubt very much if any appreciable amount of it has been compacted into tight, easily accessible seams; most of it is probably outcropping, small deposits pushed upward by seismic pressure. It's a phenomenon that's not very noticeable in the short run, but it has an effect over time. Now, to mine that material, you'd have to tear the mountain down, a prohibitively expensive task whose return probably wouldn't pay for a single day of labor and supplies. Forget about mining any further on the summit. Those heights will serve another purpose. I do have something in mind, but I'd like to save that until a bit later.
"So you think we should follow the seam downward?"
"Yes. That's the direction it's flowing. In my judgment, the real worth of this deposit, and its one of the richest I've ever seen, lies far underground. And that, my dear fellow, is where your tunnel must go."
"Essentially, yes, but indirectly, by a gradual approach. Think about the way we climbed the summit cliff this morning, as short as it was. The narrow path we followed slabbed obliquely across its slope, lessening the difficulty of the ascent. Your tunnel must do the same. But first, you must keep extending its length inby, perhaps for another half mile; losing a little more elevation, as you have at present, won't do any harm. That should bring you to the center of the mountain's base, roughly speaking, and probably to the center of the underground seam, as well. At that point, your entryway should change direction, turn left and begin curving downward in a tight spiral around the center..."
"Henry, I'm having trouble visualizing this," Frank interrupted.
"All right. Picture in your mind, then, a hollow cylinder running vertically through the center of the mountain, from the depths of the underground deposits to the summit itself... "
Bevens interrupted himself. He sensed the complaint coming before it could be spoken "Yes, I know, Frank, there's nothing inside the mountain that resembles that now, but I'd like you to consider it anyway.
"Now, divide the cylinder in two. The top portion runs from the level of the valley to the summit. The bottom half extends in the other direction, from valley level to the deepest part of the underground seam."
"And the tunnel?"
"The tunnel continues to descend in a spiral pattern on a gradual grade, coiling around that imaginary central cylinder as it moves lower into the seam. If you will, think of the entry as a coiled spring wound loosely around a metal rod. That is precisely the geometry that I have in mind."
"So we will mine our rich coal seam by digging this twisting, downward bearing tunnel?"
"A large volume of high quality coal will be produced during its construction, yes, but the real purpose of the descending spiral will be to provide a central roadway or boulevard to the main deposits underground...Let me finish, Frank, then more questions.
"The grades on the descending entry will not be uniform. Let me try to make this clearer by using a more concrete example. It will be less precise, but maybe easier to understand.
"Take a simple graphite pencil and a half dozen squares of paper or thin card stock, oh perhaps two inches long on each edge. Punch a hole in the center of each square. Now, hold the pencil in a vertical position, point facing downward, and using the holes, slide the paper squares onto the pencil, keeping them evenly spaced apart. The resulting figure should resemble a column of parallel planes, the paper squares, connected by a vertical column, the pencil."
"So where does the spiral and the column come in, Henry?"
"Ah, I thought you would ask that. But you will have to perform one more mental tumblesault, I'm afraid. The spiraling roadway is the continuous ramp that connects all the planes or levels together. It's the way you get from one level to the next. The pencil represents the column or center of the coiled spring.
"Now, each level or gallery will extend horizontally in every direction, a great distance into the seam. You might consider them to be floors in the coal mine, floors connected by a curving, descending corridor.
You can also think of each separate level as an independent coal mine. And each of these independent coal mines will have its own system of tunnels. Three or four lateral tunnels will be dug on each level, radiating outward from the center of the spiral. They will pierce the seam on that level and provide access to its furthest reaches. Of Course, the length of the laterals will vary substantially according to the horizontal extent of the seam on that level. Eventually, they might be several miles long
"Along each lateral, a complex system of rooms and pillars will be dug, extending orthogonally from either side. The configuration will resemble a bee hive, then, from a top view, if you were somehow able to remove the ceiling and float above the laterals. Just remember that it's the rooms that yield the coal and the pillars that support the ceiling or overburden. But I'm getting way ahead of myself. This stage of development won't be achieved for many years.
"I mentioned before that grades will vary along the spiral. The entryway will have to be relatively flat in the areas where it passes the intersecting entrances to the laterals; it can dip downward again as it prepares to descent to a lower level.
"Well, that's about it for now, I suppose," Bevens said, blushing more that he would have liked.
Frank and Cameron sat quietly, staring at Bevens. It was impossible to determine if they were stunned into silence or struggling to grasp the vision that the engineer had laid before them.
Finally, Frank found his voice. "Henry, that is simply amazing."
"Yes, but I've only sketched an outline and left out most of the details. There are still many problems in the plan, designing a ventilation system, providing for escape routes, and dozens of others things too complicated to consider now."
"You did, however, leave out one important consideration that must be faced now, not later."
"Yes, I know. How will you get the coal out of the mine and ship it to market."
"It doesn't matter how well we could develop the mine if we can't solve that problem now."
"Well, I think we can. Perhaps not at the moment, but soon. Within six months to a year if everything goes smoothly."
"We're waiting, Henry. We can't hold our breath that long for you to tell us."
"Remember your question earlier about the summit, whether you should resume digging up there? I had a better idea then, but I wanted to save it for the right moment. Apparently, the right moment is now.
"I suggest that you drill a vertical shaft from the summit through the center of the mine. The central shaft plays the role of the imaginary cylinder in my model of the mine's geometry; alternatively, you can think of it as the pencil in my example, a huge, very long pencil.
"The purpose of the shaft is to install a skip hoist on the summit; in order words, a mine elevator will descent to the lower levels through the center shaft. At each level of the mine, at the inset points, where the laterals intersect with the shaft, coal can be loaded onto skip cars, then hoisted to the summit, unloaded, processed, and shipped to market. Over and over again. It's the fastest, easiest way to bring your coal from the depths of the mine to the surface. It's probably the only practical method to get it to market."
"Henry, the summit is about eight hundred feet off the valley floor. And that's before you reach the first underground level. How can we drill that far? What would we use for a drill?"