accounts given what are the precise causes of such disasters, but there is reason to believe that ignorance is prolific; that many persons have only a vague knowledge of the qualities of nitro-glycerine, can not recognize it when they see it, and are not acquainted with the various forms in which it is compounded or with the peculiar dangers of handling it carelessly. Nitro-glycerine itself is a dense, yellowish liquid, but, in order to diminish the danger attending its use, fine earth, ground mica, sawdust, or some similar powder, is saturated with it, and thus the various blasting-powders known as dynamite, mica-powder, dualin, rend-rock, etc., are formed. These compounds can be transported with comparative safety. But the nitro-glycerine easily drains off from the powder and oozes from any crevice in the vessel in which the compound is kept. Drops of it thus bedewing the edges of a box may very easily be mistaken for oil escaping, and if workmen ignorantly endeavor to nail the box tighter or to open it for examination there will be a disastrous explosion. Several have occurred in past years in this way. The victims knew, no doubt, that nitro-glycerine (or the compounds) may be exploded by a blow (contact with fire is not needful), but they did not suspect that the innocent-looking oil was nitro-glycerine. Why should not youth be taught in the schools somewhat of the practical dangers of these substances which are coming into such common use? They would pursue the study with interest, especially if there were judicious experiments. A Missouri story is that a teacher confiscated a small metal box which a pupil was playing with in school hours, and, thinking it contained chewing-gum, tried to break it open with a hammer. It was a dynamite torpedo of the kind used on the railroad-track as a danger-signal, and large bits of it had to be cut out of the lady's cheek. Would it not have been well if she had known somewhat of the aspect of torpedoes? Was it not more important to the journeyman plumber who threw the lighted match into the pan of camphene, mistaking it for water, by which the great printing establishment of Franklin Square was burned some twenty-eight years ago, to know camphene by sight than to have memorized many of the matters prominent in a public-school course? Surely workmen, especially "raw hands" in establishments where these things are used, should be systematically instructed in advance, and the courts are now enforcing this principle. Two lawsuits were heard during 1880, where managers of mining companies introduced blasting-powder as a substitute for gunpowder, without specially instructing the workmen as to the change and the new precautions they ought to take. The workmen used the powder improperly, and some of them were badly hurt. The victims brought suit for damages, and the companies retorted that the disasters were due to carelessness of the men. Both courts said that the proprietors of mines have a right to introduce a more effective powder, but they are bound to give their men judicious instructions and cautions, and to furnish them with any implements or apparatus appro-
