The San Francisco call., 1898-04-17

A ing, it is not navy-yard at all, but
 a gun factory. Here it is that all the heavy guns and most of the light landing and boat guns for the navy are built The amount of work done in this great national factory is enormous, even in times of peace, but now that the lathes, engines and tools are run ming at full speed twenty-four hours out of twenty-four, the number of guns and gun carriages turned out is near ly trebled.
 Passing through the gate with its trim marine sentry pacing to and fro, the visitor sees uniformed officers has tening this way and that, busy with their duties, and hears on every side the dull rumble of machinery, the heavy thud of the triphammer, and the snorting of the steam cranes. small army of draftsmen in the offices are busily preparing plans and drawings for the use of the gun builders, and the civilian bosses and foremen of the shops are everywhere keeping watch with eagle eyes. Theirs is a most re- sponsible duty, for any careless and in- competent workman with single slip of his tool might spoil a gun or car- riage which had cost the Government thousands of dollars to put together.
 The putting together or assembling of a modern gun is apparently simple matter. But it is really one of the most delicate operations in the world. The greatest care and precision are neces- | cary to make the different parts exactly fit, and one re yolution too many of plane or boring tool would injure the part beyond repair. Hence comes much of the fascinati~ n in watching the con- Struction of one of the big guns as 1t grows in massive and polished beauty ready to take its place on one of our men-Of-War
 First of all the tube of the piece comes to the factory from one of the big steel companies, the Bethlehem or the Midvale, which have the contracts to furnish forgings. The tube comes in the rough with only core bored out. and looks like a heavy piece of steel pipe For the four-inch guns it is 13 feet inches long, while for the 19-inch guns it attains a length of 40 feet. This tube forms a basis for all future opera tions.
 A modern gun is built up by slip ping upon it a number of jackets and hoops, and shrinking them to perfect adjustment A 13-inch gun when fin ished, has thirteen separate and dis tinct parts which have been assembled and fitted to the minutest fraction of an inch. AS the caliber and size Of the gun diminishes the number of parts is reduced, and the four-inch piece is composed of only five.
 In building up the gun the rough tube 1 and the bands are first placed in latheS | and carefully planed down to the di- | mensions required. The diameter of the interior of the jacket which is to | slip over the tube half way it's length | must correspond with mathematical ex- apfnaSS tO the diameter the tubo'S | exterior; while the hoops, which in turn fit over this jacket, must be treated with like precision.
 This work of blaming is done in the great north gun shop, as it is known at the navy yard and when it is com pleted, the tube and the bands have to be carried to the shrinking pitt at the north end of the shop, where the next process is to be undergone. There are three heavy travelling cranes in the shop, of 110, 40 and 15 tons lifting power, respectively, and they pick up the huge pieces of iron and carry them to their destination as easily and lightly as if they weighed nothing at all.
 The shrinking pit is deep hole sunk in the floor of the shop, and fitted at each end with an oven. These ovens, in which the bands are to be expanded until they can slip over the gun tube, ] are H6dIGu ny dn ctlI anu OH DldSI to d temperature of 700 degrees Fahrenheit, for this degree of heat is necessary to expand the heavy jacket for the 12 and 13-inch guns. At the pit the tube is planted carefully on end close to the oven, in which is being heated the jacket that it is to receive. Pipes are so arranged that a stream of water can be run continuously through the core of the tube, to keep it cool and prevent expansion by the heat, as the hot jacket slips over it.
 When all is ready, the men who are to perform the delicate task stand at attention. Each one of them has his own particular duty, and they are trained to act in concert, like a com pany of soldiers. The jacket has been placed in the oven and sealed up, to await expansion by the heat. The fore man gives the word. the travelling crane comes up and lifts off the hot lid of the oven, exposing the jacket within, the hooks are made fast to a clamp pre- viously attached to the jacket, and the heated mass is lifted carefully from it's fiery bed.
 The engineer of the crane watches, with hawk-like eyes. the signals of the foreman below, and when a sufficient height has been reached the jacket is swung over the tube and lowered. Men with immense canvas mitten guide it
 
 When it has been slipped yer the tube streams of water are turned on to cool it. As it cools it shrinks back to it's original size, and the delicate operation is complete.
 Strange as it may seem, after coming through it's fiery ordeal the jacket hardly shows a sign of heat as it is lifted from the oven. There is a slight bluish tinge, and that is the Lnly thing to distinguish it from the cold jacket which went in. The exterior O. the tube and the interior of the jacket being ex- actly the same size, only the slightest expansion is -quired to make one slip over the her. From 3-100 to 5-100 of an inch is all that is allowed, even in the monster 13-ir h guns. So the speed jest and most accurate work is neces- sary after the jacket leaves tn. oven for if the iron should cool off before it was in place it would clamp at once upon the tube, and the gun would be ruined. A similar process is gone through with in slipping the smaller hoops over the jacket.
 The shrinking of one part on another makes an absolutely perfect weld, and after once the band is in place nothing short of chipping it off piece by piece would remove it. The shrinking of the