THOSE tremendous engines of destruction, solid pieces of steel, some of them weighing over sixty tons, what a costly piece of mechanism one of them is! Says Harper's Round Table: 'It has a chamber running nearly its entire length 13 inches in diameter. At the breech of the gun that chamber is enlarged to a diameter of 15½ inches for 6¾ feet. The long tube of the gun is strengthened by an enormous band, reaching almost half its length, and called a 'jacket,' and in addition it has what is called a hoop or band, with the appliances whereby the gun is fastened or locked to its carriage. Inside the tube of the gun there are about 50 spiral grooves, which give the projectile or long bullet a twist as it leaves the gun. That twist causes the projectile to turn nearly 75 times a second as it plunges through the air. This projectile weighs 1,100 pounds, and it requires no less than 500 pounds of powder to give it its full force. Every discharge of the gun costs in powder and projectile fully $600. The cost of one of these guns is not far from $100,000. 'To make one of these implements of war requires not only great skill, but the use of very costly machinery. Not only must the steel be cooked in enormous furnaces, but it must be seasoned as delicately as the most expensive dish for a banquet. Chemistry is called upon to say just when the metal of which the gun is made is of the proper degree of purity. Then the steel is cast into a long casting. When it is cooled it is forged or elongated under pressure while hot. Then it is 'turned' outside and inside on enormous lathes. Then it is tempered, so as to harden the metal and to distribute the molecules evenly through the mass, to prevent dangerous strains and bursting when the gun is fired. Then it is 'turned' again outside and inside with absolute accuracy as to size. Then the powder chamber is finished, and the mechanism for the fastening of the breech-block is made. Then the gun is ready for its carriage, without which, of course, it could do no work.'