Notice metal left above weld, where it flowed up into the riser.]
[Illustration: A LARGE SHAFT WELDED BY THE THERMIT PROCESS
Protruding metal is that which flowed up into gate and riser. It is cut away by the gas torch to leave a neat weld.]
CUTTING UP THE OLD BATTLESHIP MAINE WITH AN OXY-ACETYLENE GAS TORCH
Picture shows end of boat crane over exploded magazine, which was cut off in fifteen minutes.]
Oxygen and acetylene generators can be seen on top of after-turret.]
Things move with a rush now, for all these arrangements are made ahead of time, and as soon as the workmen are sure that the parts in the mould are redhot the heating aperture is carefully plugged with fire sand and the thermit is ignited. From a mere pinch to half a teaspoonful of the ignition powder is put into a little hollow in the thermit so that the heat may be communicated at once to as much of the thermit as possible. This is then set off with a storm match. The workman quickly withdraws his hand, slams the lid on to the crucible and gets out of the way of flying sparks.
There is a hiss, a puff of white smoke, a blinding glare from the hole in the top of the crucible, and that is all, beside a few sparks, to indicate that a heat second only to that of the sun is being generated within.
One cannot help but marvel at the wonders of science as this inconceivable heat is being produced, the process is seemingly so simple, so easily handled, and so accessible for all kinds of work where steel welding is necessary.
Half a minute to a minute (according to the amount of thermit used) after the match has been applied a workman holding at arm's length a long tool called a "tapping spade" gives a few upward knocks to the little metal pin extending down from the closed pouring aperture. He jumps back for the heat is enough to set his clothes afire, even at a considerable distance, and a few flying particles of the molten thermit would inflict a serious burn.
Down through the little hole the thermit, that a minute before had been only a coarse dark gray powder like metal filings, seemingly the last thing on earth that would catch fire, flows into the pouring gate of the mould in a steady stream of white-hot liquid steel. The white glow from the metal is brighter than any electric light. It is so intense that although the workmen wear heavy dark goggles, they shade their eyes and turn their heads away.
