from The Century Dictionary.
- noun A passage in a mine made or used for ventilating purposes; an airway.
Sorry, no etymologies found.
He explained that by reversing the fan they could draw the smoke up through the air-course, which would clear the main passages for a time.
The girls had followed this procession in an air-course that exactly paralleled the trail.
"One time in Cedar Mountain we go see boss, say air-course blocked.
"Don't ye remember the time when the air-course was blocked before, and ye helped to get up the mules yeself?