-on the ship-carriages, at high elevations, that the breech of the gun was raised, and came down again with a considerable blow on the quoin or elevating screw. If the chase of the gun is light, the muzzle will sometimes be broken

off, instead of overcoming the inertia of the gun, or lifting the breech suddenly, against the resistance of the preponderance.

82. This result would occur with more certainty if the whole interior metal of the gun were heated and expanded laterally and longitudinally, straining the gun to the extreme verge of its strength to resist. This example is inserted as one of the peculiarities of living force, as exhibited in gunnery, viz: resistance to changes of direction by bodies in motion, and to account for the failure of many of the Dahlgren and Parrott guns, from the breaking off of their muzzles, as has frequently happened since the war began.

83. In 1855 I made a heavy pile-hammer in Chicago, for a contractor on the Illinois and Michigan canal, which was removed from the mould in the foundry too early, and placed on a paving of brick on the deck of a canal boat for transportation to Joliette. It was so hot when put on board that it set fire to the deck about two hours after, while en route. In dashing water under it upon the deck, some was thrown upon the hot iron, cooling parts in advance; at a later time when the heat left the interior, it burst in two parts, and each piece was thrown to the bow or stern, and passing down through the bottom, sunk the canal boat. The report was heard two miles.

84. One of Blakely's first guns, as exhibited in the following diagram, failed by the longitudinal extension of the inner tube, and the bands between the trunnion ring and the cascabel. The gun was strengthened longitudinally by four bolts, reaching from the trunnion ring to a cascabel piece against the breech of the gun.

*

85. Captain Blakely says of this accident: "At this round the four bolts gave way the four united being equal to a solid bar the size of the bore. The rest of the gun was uninjured. I had this gun re-made with four bolts of the best charcoal iron, but they, too, broke without injury to the tubular part."-Paper read by Captain Blakely before the United Service Institution, England; vol. III, Journal.

86. There is no way to account for this except by the extension of the length of that part of the gun sustained by the bolts, by heat; if the pressure of the powder had broken the bolts, the whole breech would have been shot away. It is satisfactory to us in this manner to learn that in England they do not know the cause of the failure of guns; we may thus now far excel them, if we utilize the knowledge we have.

87. The inner tube of the Whitworth gun shown in General Gilmore's report increased in length one inch, (shown marked a b on the cut,) by the heat communicated to it, and closed the vent. If the bands had been fastened by screw threads, as recommended by Prof. Treadwell, and by General Gilmore, the bands would have parted transversely as d1 the bolts of the Blakely gun.

There are two views of this gun in General Gilmore's book, a slight mark on the reinforce would lead us to suppose the reinforce had been cracked transversely. It is strange that the other view should be one of the opposite side of the gun, and that nothing should be said of the crack.

88. A three hundred pounder Armstrong gun, in which the breech piece was inserted by screw threads within the principal reinforce band abutting against the inner tube of steel, was burst by the lengthwise expansion of the inner tube, pushing out the whole breech, breaking the reinforce band transversely, (cut on left side.) Compare this example with the Whitworth gun shown in Gen'eral Gilmore's report and with those Parrott's that have failed at the breech, (see cut to right,) and see the analogy.

89. When a Parrott gun is strained radially as well as longitudinally forward and under the band by the heating inside, the reaction of the forces having a tendency to push out the breech also tend to push outward and forward the slab of the cast-iron reinforce that leaves the gun forward of the band or wroughtiron hoop, and in this effort the pressure of the powder assists; hence the forward reinforce fractures, and when the band also breaks, the cause is obvious.

300 pouuder Armstrong gun, breech pushed out by extension of inner tube. Par. 88.

Parrott gun breech ferced out by same cause.

90. An Armstrong gun, a banded tube, failed by the breaking of the outside band. If the pressure of the powder had broken it the parts would have been thrown off with projectile force.

81. Here we have five guns, exhibiting the effect of the expansion of the inner metal of guns by heat of the powder to the extent of rupturing them, and the most astute of our ordnance officers will find it difficult to account for the result in any other manner.

92. In the conclusion of this part of the subject, I repeat here what I have before said in the Intelligencer, to exhibit the danger of relying on the faulty guns we have now in service.

94. The Dahlgren gun is a shell gun, and is the most beautiful gun in any service in the world, but it is believed that more effective guns are now required for attack on iron-clad ships. The first Monitor was armed with guns of this class; and great reliance was placed on them in case that certain wrought iron solid projectiles, prepared for them, were to be used in any encounter with the Merrimac; but it is understood that the inventor forbade the use of the latter, even with the fifteen pound charge of powder. Lest his directions should not be obeyed, it is said that he caused them to be taken off the Monitor, while she was at anchor in Hampton Roads, and certain other hollow shots, covered with bronze, substituted. Shells broke against the sides of the Merrimac, inflicting no injury. Hence the Merrimac continued to be the terror to our army and navy for a long critical time. But for this we might have captured Richmond sooner than we did Yorktown; and who can conceive or estimate the cost of life or money that has resulted?

95. Other eleven-inch shells have been projected against iron sides without effect. We must have better guns than these to meet the requirements of modern naval warfare.

96. Next we have the Rodman fifteen-inch gun, cast hollow, and cooled from the interior, the object attained by which is to freeze the metal from its liquid state immediately surrounding the bore first. As the heat is nearly all withdrawn from the cast block through the surface of the bore, successive strata of the iron freeze and contract upon the stratum within it, having the effect to contract or squeeze it into smaller dimensions, both longitudinally and radially. In this manner the state of "initial tension" is attained in the gun, which makes it capable of resisting a greater pressure from within, having a tendency to rupture the wall or enlarge the bore of the gun; the necessity for which tension has been beautifully described and illustrated by Professor Treadwell, of Harvard, and by Captain Blakely, R. A., England. Although the longitudinal tension might be considered advantageous in assisting to resist the lengthwise pressure of the powder against the bottom of the bore or chamber of the gun, there is another rupturing force to be provided for, viz: the unequal heating when it is fired; for then this force has the tendency that cannot be resisted by any amount of strength in the gun to increase both the longitudinal and radial

extension, for the part even slightly heated becomes both longer and larger in diameter.

97. The Rodman gun, as cast at the great Fort Pitt foundry, is strained in this manner to the extreme limit of the elasticity of the outside metal, and to the extreme limit of compressibility of the inside metal, which is proved by the fact that one of them was ruptured at the above-named foundry, from end to end, before it was removed from the mould in which it was cast; and the fissure, occurring through a wall of iron sixteen inches thickness and about sixteen feet in length, remained in the close contract along the bore, while it was gaping along the outside wide enough for the insertion of the fingers. Like St. Rupert's drops, these guns are liable to fly into pieces on slight occasions. How wonderful it is that any of them endure firing at all.

98. If a tightly-fitting tompion happens to be placed in each of the large number of them mounted in the forts of New York harbor, when for some time the weather has been warm, and then changes suddenly to extreme cold, it is quite possible a number of them may be found bursted. The tompion would protect the surface of the bore from the change of temperature, which would dangerously contract the outside upon the inner metal. We have never noticed whether these guns are furnished with tompion or not. If they are, we would advise that they be not used.

99. Guns with "initial tension" can withstand more pressure than without. Consequently, a single very heavy charge can be fired from these guns without bursting them, while rapid firing, such as practiced in battle, will burst them even with small charges. When these guns are proved, as well as in target practice, they are fired slowly. If we ever have to resist the entrance to our harbors of a fleet of iron-clads each gun will have to be fired rapidly. What if they burst at that critical time? No fort or works on which these guns are mounted has ever been attacked. They have never been subjected to the test of actual battle, yet hundreds of them are being mounted on. the works at the entrances to our most important sea-port, and we rest in fancied security because they look formidable.

100. Of those mounted in our turret-ships, we believe eight were in the encounter with Fort Fisher, and two of the eight burst under the most rapid firing they have yet been subjected to. The navy-charge for these guns is thirty-five pounds of powder, with a shell of three hundred and fifty pounds, or a shot of four hundred and fifty pounds, which is a very small charge, and usually they are fired once in fifteen minutes. The velocity of the shot is so low that the effect is not what was promised or expected of them. Of the only two shots we know to have hit the sides of an iron-clad, one struck the pilot-house of the Atlanta, and one struck the Tennessee, but neither accomplished much.

101. Twenty-three large Parrott guns-burst on Morris Island in 1863, under General Gilmore, yet this alarming failure has not hindered the continuance of their supply. Before that time six had burst in the navy, beside a great number that were disabled, and in 1864 about thirty-three have burst in the navy, of which eighteen failed in Admiral Porter's fleet; perhaps there were more, for the admiral reported that all the rifled guns in the fleet had burst. At the time of the encounter with the iron-clad Albermarle, it was reported that one hundred-pound Parrotts were useless against plating with ten pounds of powder. Now it is proposed to reduce the charge to eight pounds, which must vastly diminish their value.

102. The Parrott gun embodies "initial tension" also under the band. When fired rapidly the inner metal is expanded lengthwise and radially; when so strained a slight shock will break it. The rapid firing off Fort Fisher was too much for them.

103. On Morris Island, the guns were fired mostly at high elevations; under such circumstances the pressure and temperature of the gasses is higher, and