418 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



The number placed in one channel can be as great as desired, but the size 

 of the fort, or the number of guns for each fort, should not be increased. 



The foundation may be on a rock bottom or on piling. The stone woi'k 

 could not be injured by an assault, for it is practicable to cover its small 

 exposed surface with plating that would resist any shot. The piles driven 

 about it would be a sufficient harbor breakwater, and the loose I'ock 

 deposited about its base would insure safety against an assault by rams. 



The men and magazines are placed below, so as to be protected, and the 

 turret may be of any required thickness. There is no opening through 

 which the smallest projectile could enter, and no men in the turret to be 

 injured if there were. The guns are absolutely safe from bursting, and of 

 a size to throw a projectile that would crush any ship that can be floated 

 into a harbor. I offer it as an impregnable fort with irresistible guns. It 

 (;an be constructed in less time and at less cost than anj'^ equally efficient 

 means of defence. 



Tiie hour for adjournment having arrived, Mr. Wiard proposed to con- 

 tinue his remarks at the next meeting. 



Mr. Edward Cooper asked leave to interpose an explanation of his 

 position on the rupture of heavy guns; claiming that he, rather than Mr. 

 Wiard, was entitled to the ci-edit of the discovery, and inviting the atten- 

 tion of the authorities to the fact that heat rather than strain was the 

 cause of the rupture of large guns, 



Mr. Wiard briefly explained his theory, averring his belief that he was 

 the earlier discoverer, and related some of his experience and failures in 

 making steel 50-pounders. He used the same form of gun with this 

 material as Captain Dahlgren has used successfully with cast iron. They 

 worked well on firing a great number of times slowly, but on firing fast, 

 while the exterior was cold, and in cold weather, all soon burst. He 

 believed it due to the heat on the inside expanding, the middle remained 

 small as at first. Two burst on the ninth round each. Steel differs from 

 cast iron in this respect. The Rodman system of casting iron around a 

 cool core is, however, more like a steel gun. 



Mr. Cooper asked if guns at the battle of Malvern Hills were fired by 

 their heat alone. 



Mr. Wiard did not believe this ever had occurred. 



Mr. Clinton Rosevelt presented a theory of his own in regard to the 

 explosion of guns: he averred that the rupture began on the inside, and 

 could not, therefore, be produced by heat. 



, Mr. Wiard maintained his previous opinion, and thought it was proved by 

 the fact that the modern tapering (Dahlgren) gun is hot on the outside, 

 first at the muzzle where it is thin, and that the heat comes to the sui'face 

 at other points in lines directly proportional to its increased thickness of 

 metal. 



Mr. Wiard exhibited diagrams of a cross section of a cylinder, to answer 

 the objections of Mr. Rosevelt. The fracture begins on the inside. 

 This would seem to prove that guns burst by pressure rather than by 

 expansion of the inner metal — as if the inner metal were expanded by 

 the communication of heat before the outer metal gave way — a strain of 

 compression resisted by the strength of the outer metal would rest upon the 



