Chapter 16—A Final Threat On that day, in the colliery of New Aberfoyle, work was going on in the usual regular way. In the distance could be heard the crash of great charges of dynamite, by which the carboniferous rocks were blasted. Here masses of coal were loosened by pick-ax and crowbar; there the perforating machines, with their harsh grating, bored through the masses of sandstone and schist. Hollow, cavernous noises resounded on all sides. Draughts of air rushed along the ventilating galleries, and the wooden swing-doors slammed beneath their violent gusts. In the lower tunnels, trains of trucks kept passing along at the rate of fifteen miles an hour, while at their approach electric bells warned the workmen to cower down in the refuge places. Lifts went incessantly up and down, wo