Powerful as these guns appear to be, their big brothers in the revolving turrets are far more so. While not so nimble in action, the great power of these guns of the main battery, and the elaboration and completeness of mechanism for operating them, for supplying them with ammunition, and for rotating the turrets, constitute a complete world in ordnance in itself. As the gun increases in size, its cost both in construction and service increases in a greatly disproportionate ratio. A 6-inch breech-loading rifle costs $64.40 for each discharge, while a 12-inch gun costs $458 for each discharge. The largest guns of our battleships are of 13 inch calibre, and about 40 feet long, but larger ones are employed for sea coast defenses. The great 16-inch 126-ton gun, now building for the United States at the Watervliet arsenal, is 49¼ feet long, over 6 feet in diameter at the breech, and it will have an extreme range of over twenty miles. Its projectile will weigh 2,370 pounds, and it will cost $865 to fire the gun once. The accompanying view, Fig. 270, will give graphic illustration of the range of this gun. If fired at its maximum elevation from the battery at the south end of New York in a northerly direction, its projectile would pass over the city of New York, over Grant’s Tomb, Spuyten Duyvil, Riverdale, Mount St. Vincent, Ludlow, Yonkers, and would land near Hastings-on-the-Hudson, nearly twenty miles away, as shown in our map, Fig. 271. The extreme height of its trajectory would be 30,516 feet, or nearly six miles. This means that if Pike’s Peak, of the Western Hemisphere, had piled on top of it Mont Blanc, of the Eastern Hemisphere, this gun would hurl its enormous projectile so high above them both as to still leave space below its curve to build Washington’s Monument on top of Mont Blanc, as shown in Fig. 270. [Illustration: FIG. 271.--RADIUS OF ACTION OF SIXTEEN-INCH GUN.]