Another interesting thing about the slag from chromium thermit is that small rubies have been found in it. The scientific explanation is that they are nothing but crystallized alumina, coloured with chromium. The jewels usually are too small for any commercial purpose but serve as a very striking example of the intensity of the thermit fire. All the real jewels, diamonds, rubies, emeralds, amethysts, and so on, were formed by the terrific heat in the bosom of the earth millions of years ago when it was cooling down from gases hotter than anything we can possibly conceive of, to a molten ball, then to a solid redhot mass and then to a globe sufficiently cool on the outside to be crusted over. That they can be made in this little chemical furnace shows how far science has gone in imitation of the wonders of nature. AUTOGENOUS WELDING AND CUTTING "Now," said the scientist, after he and his young friend had finished some experiments, and were ready to talk about autogenous welding, "imagine a little white flame no bigger than a pencil point at the end of a brass pipe about the size, and not entirely unlike in appearance the old-fashioned taper holder with which you used to light the gas, and you have before you in the rough, a picture of one of the oxy-acetylene torches that will in a few minutes weld two pieces of almost any metal, or in a few seconds cut a solid plate of the hardest steel of several inches thickness almost as fast and easy as a carpenter could saw a board, and yet without taking the temper out of the metal." Picking up what seemed to be a little brass rod bent at the end, the man turned a valve, applied a match, and as the gas burned up with a beautiful little flame of dazzling whiteness, he continued: "This tiny flame, so easily controlled, is hotter than any produced by man except that generated by the electrical furnace, for it reaches a temperature of about 6,300 degrees Fahrenheit. Previous to the invention of these wonderful torches the oxy-hydrogen was the hottest gas flame, but it only reached a temperature of 4,000 degrees Fahrenheit." "How do you use it?" asked the boy. "Well, for instance, Uncle Sam is enabled to weld and cut steel plate in building his battleships, steelworkers to carry on their gigantic tasks, and wreckers to clear away tangled masses of steel beams far more quickly and easily than with the older methods.