There was a wire-haired and almond eyed Korean, named Cho, a “rope-rider” in Hal’s part of the mine. He was one of those who had charge of the long trains of cars, called “trips,” which were hauled through the main passage-ways; the name “rope-rider” came from the fact that he sat on the heavy iron ring to which the rope was attached. He invited Hal to a seat with him, and Hal accepted, at peril of his job as well as of his limbs. Cho had picked up what he fondly thought was English, and now and then one could understand a word. He pointed upon the ground, and shouted above the rattle of the cars: “Big dust!” Hal saw that the ground was covered with six inches of coal-dust, while on the old disused walls one could write his name in it. “Much blow-up!” said the rope-rider; and when the last empty cars had been shunted off into the working-rooms, and he was waiting to make up a return “trip,” he laboured with gestures to explain what he meant. “Load cars. Bang! Bust like hell!” Hal knew that the mountain air in this region was famous for its dryness; he learned now that the quality which meant life to invalids from every part of the world meant death to those who toiled to keep the invalids warm. Driven through the mines by great fans, this air took out every particle of moisture, and left coal dust so thick and dry that there were fatal explosions from the mere friction of loading-shovels. So it happened that these mines were killing several times as many men as other mines throughout the country. Was there no remedy for this, Hal asked, talking with one of his mule-drivers, Tim Rafferty, the evening after his ride with Cho. There was a remedy, said Tim--the law required sprinkling the mines with “adobe-dust”; and once in Tim’s life, he remembered this law’s being obeyed. There had come some “big fellows” inspecting things, and previous to their visit there had been an elaborate campaign of sprinkling. But that had been several years ago, and now the apparatus was stored away, nobody knew where, and one heard nothing about sprinkling. It was the same with precautions against gas. The North Valley mines were especially “gassy,” it appeared. In these old rambling passages one smelt a stink as of all the rotten eggs in all the barn-yards of the world; and this sulphuretted hydrogen was the least dangerous of the gases against which a miner had to contend. There was the dreaded “choke-damp,” which was odourless, and heavier than air. Striking into soft, greasy coal, one would open a pocket of this gas, a deposit laid up for countless ages, awaiting its predestined victim. A man might sink to sleep as he lay at work, and if his “buddy,” or helper, happened to be out of sight, and to delay a minute too long, it would be all over with the man. And there was the still more dreaded “fire-damp,” which might wreck a whole mine, and kill scores and even hundreds of men.