The extra pipe is the same size as the others and extends down to the end of the torch at an angle where its tip is clamped alongside the main tip. The rear end of the third tube is connected with a rubber hose like the others, which extends to the oxygen tank. The flow of oxygen is under higher, and individual working pressure, controlled by a valve. In a new style torch the extra hose is done away with and the separation of the oxygen is done in the torch. When the modern steel carpenter wants to cut a hole, or saw off a strip from a piece of steel, no matter whether it be a steel beam, steel plate, or almost any other form of iron (except cast-iron), he attaches the cutting pipe, lights his torch and sets to work. Holding the tool about half an inch from the surface he directs the little blue flame, which is no more than three quarters of an inch long, and a quarter of an inch thick, against the spot where he desires to start cutting. He holds it there a few seconds, then there is a shower of sparks on the under side of the steel plate, indicating that the flame has eaten its way all the way through. The operator next moves the torch along the line where he wants to cut. The speed with which he can move is governed by the thickness of the steel to be cut. Half-inch ship steel, for instance, could be cut at a rate of more than a foot a minute. The heat of the flame melts a little of the steel, which drops down in molten particles, but the edge that is cut is sharp and clean, and its temper is as perfect as if the cutting were done with one of the laborious old-fashioned steel saws. [Illustration: AN OXY-ACETYLENE GAS TORCH WELD Note the little torch in the man's left hand, the filling metal in his right, and the inserted picture of the apparatus.] [Illustration: TINY 200-HORSEPOWER TURBINE This engine could almost be covered by a derby hat. A part of the casing is removed to show the smooth disks.] [Illustration: THE TESLA TURBINE PUMP Driven by a 1/12-horsepower motor. The little pump here shown is delivering 40 gallons of water per minute against a 9-foot head.] This cutting process is of especial value to navy yards, shipyards, and wreckers, where there is a great deal of steel to be cut. Uncle Sam uses it at most of his navy yards, for in building his battleships there are thousands and thousands of holes to be cut in steel plates, plates to be shaped, and beams to be cut off to required lengths.