Half an hour’s work with a chisel and hammer sufficed to enlarge the holes.  They then filled up the trays with more soot and firelighters, kindled a fire, and when the smoke began to surge, ran the machine out at the gate on to the high-road.  A winding hill, nearly half a mile long, led down to the village.  The slope was not very steep; the tricycle with its tank was heavy, and the bearings rusty; but by dint of hard pedalling they soon worked up a good speed, and the increased draught caused the smoke to pour forth in a dense cloud, ever increasing in volume and pungency.