A still more simple apparatus has been invented by Monsieur Galibert. The system for condensing the pure air is more perfect, while the reservoir consists of a well-prepared goat-skin, which, when inflated, a man can with ease carry on his back. It is furnished with a similar contrivance to the former, a tube passing from the reservoir to the mouth, while the nostrils are compressed, the eyes and head are protected, so that provided with it, a person may exist for a quarter of an hour in the foulest atmosphere, or in the midst of dense smoke. Although the metal miner is subjected to fewer accidents than are his brethren working in coal mines, the atmosphere in the former is far more destructive to human life. In lead mines, the duration of life averages scarcely more than thirty-two years, and in those containing arsenical pyrites or quicksilver ores, the average is still lower. Before the use of gunpowder in underground operations, the rocks containing the ore were attacked with fire, indeed the practice is still retained in some countries. Huge wood fires are made up against the face of the rock, which becomes shattered and traversed by cracks, and when cooled, it is easily detached with a pick or fork. Of late years, however, machines have been devised for boring or breaking the rock. Some form a hole by the continuous motion of a rotating drill, others by means of intermittent blows. One of these rock-boring machines, manufactured by Messrs. Turner, of Ipswich, performs its work by a combination of both these operations. By the employment of these machines, the formation of the tunnel under Mount Cenis was greatly facilitated. An example has already been given of the way in which people have been saved from the effects of inundations in mines, others have been dug out when buried by the fall of roofs, but almost countless are the numbers who have perished from other causes, for if the first have destroyed their hundreds, the fire-damp in coal mines has proved the destruction of thousands. It was at one time considered right every night to provoke an explosion by lighting the fire-damp in order that the working stalls should be accessible next morning. The man who performed this dangerous operation wore a thick covering of wool or leather, his face was protected, and his head was covered by a hood like a monk's cowl. He crept along the ground, carrying in his hand a long pole with a light at the end of it. He was known in the English mines as the fireman, but in the French he was called either the cannonier, the monk, or the penitent, the latter name being given him from his dress resembling that of certain so-called religious orders in the Romish Church. Too frequently the hapless penitent was destroyed by the explosion he had provoked.