Men go down into the ground and dig out the coal, and steam-cars take it to the large cities, and sell it to people to burn, to make them warm and happy when it is cold out of doors.
Quicker or slower, the water that fills it will wash in sand and mud, and year by year this process will go on till ultimately the whole reservoir is filled up. The embankment is raised, and raised again, but at last it is better to abandon it and make a new tank elsewhere, for it would never pay to dig out the silt by manual labour.
Hilly plateaus are still in the same geological phase, and are dotted with numberless lakes and ponds, while the rivers continue to dig out their yet undetermined channels.
Zeb called to them, you must dig out and race until you reach those three trees you see over yonder.