"They do just two things; they haul coal to the bottom of the inclined shaft, where it must be reloaded--at wholly unnecessary expense--in order to be hauled by machinery up the incline to the surface. Half the time they are employed in hauling water. The mine, you must understand, declines from the foot of the shaft to the end of the main heading. The very lowest level of all is there, where I propose to put in a ventilating shaft, with a fan; all the water flows to that point, flooding it. Under the antediluvian methods in use in this mine, all this water must be pumped into leaky cars and hauled by mules to the bottom of the the sloping shaft, whence it is drawn up by the engine, spilling half of it before it reaches the surface. Now, when I sink that ventilating shaft out there on the prairie, I must have an engine to turn the fan. Very well, I've got it. Among the junk that Captain Hallam bought when the war ended and the river navy went out of commission, there are parts of many little steam engines. I've busied myself at night in measuring these and fitting part of one to parts of another. The result is that I have made an engine out of this rubbish, which will not only drive the ventilating fan, but will also pump all the water out of the mine." "But will not the mules be needed for hauling coal to the bottom of the shaft?" "Not at all, if you are willing to spend a little money in an improvement--say a fourth or a third of what the mules will bring in the market--or considerably less than it costs to feed and curry them for a year." "What is the nature of the improvement?" "Why, simply an extension to every part of the mine of the cable system by which the engine now hauls the coal and water up the slope." "But where are we to get power?" "By using what we already have. Our great engine is a double one. We are using only one of its cylinders. We have only to connect the other in order to have all the power we need." "But what about steam?" "That's easy to make. We have several unused boilers, and as we burn nothing under our boilers but culm--the finely slaked coal for which there isn't a market, even at a tenth of a cent a ton--it will cost us absolutely not one cent to make all the steam we need." "You seem to have thought it all out." "I have done more than that. I have _worked_ it all out. I must work all day in a heading, of course, in order to make bread and butter. I have worked at night over these problems." "And you are sure you've got the right answers?" "Greatly more than sure--absolutely certain!"