UNITED STATES NAVY. 



795 



in giving the exterior portion of the gun a cer- 

 tain initial tension, gradually decreasing toward 

 the interior, and giving to the interior parts a 

 certain normal state of compression by the 

 shrinkage of the outer jacket and hoops. The 

 tube or body of the gun is a single forging, 

 extending almost the entire length of the gun. 

 Over the rear portion of the tube is shrunk a 

 jacket extending about two fifths of the length, 

 and over the remainder of the tube and over 

 the jacket is shrunk a series of hoops, all the 

 parts being locked together so as to form an 

 extremely strong structure. The breech-clos- 

 ure screws into the jacket. The tube and jack- 

 ets are made from solid steel ingots, forged, 

 tempered in oil, annealed, and bored and ma- 

 chined to the required dimensions. The hoops 

 are forged upon a mandrel, and subsequently 

 treated in the same manner as other forgings. 

 To shrink the jacket on the tube, the latter is 

 placed vertically in a pit, breech, end up, and 

 after heating the jacket to a temperature suffi- 

 cient to expand its interior diameter to the 

 required amount, it is lifted by a crane and 

 dropped over the tube. The hoops are then 

 shrunk on, and finally the trunnion-band is 

 screwed on in place, which also assists in lock- 

 ing the parts together. The gun is then ready 

 to be rifled, and afterward to have the breech- 

 closure and sights fitted. The following are 

 the requirements for material for 6-inch and 

 8-inch guns: 



The powder-pressure is usually about 15 

 tons to the square inch, but the guns may be 

 safely fired under a pressure of 22 tons. 



Recently manufacturers of steel have claimed 

 that solid steel-cast guns are preferable to the 

 built-up gun before described. In order to test 

 the claims of these, Congress authorized the 

 construction of three steel-cast guns the first 

 to be made of Bessemer, the second of open- 

 hearth, and the third of crucible steel. Pro- 

 posals were received from two firms the Pitts- 

 burg Steel- Casting Company for the Bessemer 

 gun, and the Standard Steel-Casting Company, 

 of Thurlow, Pa., for the open-hearth gun. Xo 

 proposals were received for the gun of crucible 

 steel. The Pittsburg gun exploded on firing 

 the first round under service conditions ; the 

 Thurlow gun successfully underwent the trial 

 of ten service-rounds, fired as rapidly as possi- 

 ble. The test of material for the Pittsburg 

 guns showed very poor characteristics ; that of 

 the Thurlow gun very fair characteristics. But 

 a comparison of the weights of the steel-cast 

 gun and the built-up gun shows their relative 

 weight to be 13,000 to 11,000 pounds. Mo na- 

 tion has yet adopted the steel-cast gun for the 

 armament of vessels or forts, the material be- 



ing considered too uncertain, and the increased 

 weight objectionable. 



Gunpowder. In the improvement of gunpow- 

 der probably lies the principal field of devel- 

 opment of gun-power. Great improvements 

 have already been made, and study and experi- 

 ment are being devoted to this question. The 

 initial velocities of projectiles in 1870 ranged 

 between 1,100 feet and 1,300 feet a second, 

 while at present initial velocities of guns in 

 service rise to 2,000 and 2,100 feet with a 

 pressure of but 15 tons to the square inch, and 

 powders recently fired in Germany and France 

 have again raised this velocity to 2,400 and 

 even 2,600 feet with the moderate pressure of 

 15 to 16 tons. Much attention is being directed 

 to the production of a powder that shall give 

 a high initial velocity with low pressure, and 

 yet be comparatively smokeless. By the em- 

 ployment of gun-cotton and picric powders, 

 much has been accomplished in Europe in this 

 direction. But the new powders are less stable 

 than the old, and doubtless deteriorate under 

 influences of heat or moisture. The powders 

 for United States naval guns (and each caliber 

 has a powder whose exact quality is peculiar to 

 itself; have been developed and manufactured 

 by the Messrs. Dupont, near Wilmington, Del. 



Pnyettiles. Ordinary shells are still made of 

 cast-iron, but armor-piercing projectiles are 

 made of steel, forged and highly tempered. 

 The manufacture of armor-piercing projectiles 

 has been developed chiefly in France, and has 

 introduced another important element in the 

 relation between the resistance of armor and 

 the capacity of the gun for penetration. So 

 perfect is the manufacture of these projectiles 

 that, when fired under service conditions, they 

 perforate the best armor-plate of a thickness 30 

 per cent, greater than the caliber of the project- 

 ile, and remain practically undeformed. The 

 bursting-charge even in ordinary shells is com- 

 paratively small for 6-inch, 5 to 10 pounds ; 

 for the 16-inch (weighing 1,800 pounds), 179 

 pounds. This has given rise to a further 

 development of the destructiveuess of shell- 

 fire by introducing high-explosive shells, whose 

 bursting- charges are dynamite, explosive gela- 

 tine, gun-cotton, or melinite. Shells loaded 

 with 500 pounds of dynamite and explosive 

 gelatine are safely fired from the Zalinski dyna- 

 mite-gun. Gun-cotton is used as a bursting- 

 charge in Germany, while the French use meli- 

 nite as a burster for shells fired from service- 

 guns under service conditions. High-explosive 

 shells, however, are quickly detonated if the 

 surface hit offers fair resistance, and for this 

 reason armor is coming much more into vogue 

 and is being more distributed over the sides of 

 vessels than has recently been the practice. 

 Four inches of armor are said to be sufficient 

 to cause the detonation of high-explosive shells. 

 The ordinary side-plating of ships is not suffi- 

 cient to detonate these, and the destructive 

 effects of their explosion within a ship are ap- 

 palling. 



