Science has not left the burglar weaponless, however. The progress accomplished has merely compelled him to obtain higher qualifications, and in the continuous strife between the armor plate and the desperado who would pierce it the thieves have had hitherto the last word. For many years dynamite was their chief reliance, and then a product was discovered some years ago by a chemist, who gave it the name of "thermit," by which the cracksman was able to melt sheet metal, inches thick, with comparatively little trouble. MELTS HARDEST STEEL. This substance known as "thermit" is in current use for repairing, heating or soldering large pieces of metal and consists of a mixture of aluminum and oxide of iron, the latter being replaced, according to the requirement, by oxide of lead, peroxide of sodium or peroxide of barium. This composition is thoroughly mixed together, or is used in the form of cartridges or tablets, which ignite by means of a piece of magnesium fixed in the substance like a wick. The heat developed is more than sufficient to cause the hardest steel to melt. Although this process is rapid and silent and really marvelous from the point of view of the result obtained, it is not without much danger to those using it, for at the high temperature produced by it an inexperienced operator runs the risk of being seriously burned. In consequence the prudent and careful burglar uses accessories which render him secure against such accidents. He protects his eyes by means of heavy dark glasses, wears shields of aluminum over his hands and applies the mixture through a small hole in the bottom of a crucible. When the reaction takes place it lasts long enough to allow the operator to charge the crucible again and again in proportion as the melting of the metal plate is effected, thus making an opening of the desired size in the safe. It is a simple enough operation for a skilled burglar, but a very dangerous one for an amateur. TESTS WITH ELECTRICITY. But even this has been discounted by an experiment before a United States government commission, showing that electricity can be so applied as to give the scientific cracksman a greater field for operation than ever before. The experiment was made by an expert burglar, who, having retired from business after amassing a sufficient competency, was requested to favor the commission by contributing the light of his knowledge. He demonstrated that by the aid of electricity he could, within a short time, reduce safes of the highest repute to old iron. For this purpose he took out of his pocket a style in the form of retort carbon, similar to those used for arc lamps; a few yards of electric wire, black eyeglasses and a plate pierced in the middle. It was with this simple outfit he pierced in less than three minutes a circle of holes in a cast steel safe with walls one and a half inches thick.