620 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



as to absorb the momentum, the result will be different. If the velocity of 

 the moving body is low it will on striking rebound; but if the velocity id 

 high it will be shattered in pieces, and the resisting body will be broken 

 also, at the point of impact. Now, suppose the stationary body has less 

 hardness, the moving body will penetrate it, but with a constantly de- 

 creasing speed, because its motion is being transmitted to the yielding 

 substance. A force capable of producing fracture may be transmitted 

 through a hard substance to a soft one, but not through a soft to a hard 

 substance. If we apply this principle to the armor of a ship we shall see 

 that the most efficient mode of resistance would be not to place iron out* 

 site of wood, but to reverse this position. This principle had been tested 

 at the request of the speaker by the Department at Washington, and wag 

 soon after substantially adopted in the construction of the Government 

 vessel Onondaga, by Mr. Quintard, at Greenpoint. Some have condemned 

 the plating advocated by the speaker, principally on the ground that shell 

 would blow it off. He therefoi*e proposed to meet this objection at the 

 next meeting of the Association.- 



The Chairman directed attention to the term homogeneous iron, used by 

 some English manufacturers. It is not a proper term to use in that con- 

 nection, because the quality of the iron, even in the same mass, will vary. 

 It may be that by the peculiar process of working blooms, a greater uni- 

 formity of texture can be secured than is found in ordinary iron, but the 

 very fact that large masses must be made up from smaller ones, forbids 

 the use of that term in its true signification, as applied to iron. 



Mr. Bartlett alluded to the experiments showing that iron is stronger in 

 the direction of its rollirjg, 



Mr. Dibbin said that the best iron used in this country is the American 

 charcoal iron. It is claimed to be manufactured entirely with charcoal, 

 but in most cases about fifty per cent, of anthracite is used, and probably 

 with little or no detriment to the quality of the metal. The value of the 

 different qualities of iron has been fully tested by the late Robt. L. Stevens, 

 of Hoboken, and his brother. This was a preliminary step in their con- 

 struction of an iron-clad ship. The homogeneous metal spoken of is rolled, 

 as well as hammered. It is simply a mild steel. It is piled together in 

 small blooms, and is consequently of a more uniform quality. 



Mr. Disturnel believed the quality of iron depended more upon the quality 

 of the ore than the manner of working it. He read a statement of Prof. 

 Johnson with regard to the comparative strength of iron made from differ- 

 ent ores, and spoke of the great tensile strength of the metal made from Lake 

 Superior ores. 



Remarks, for which we have no room, were made by Messrs. Garvey, 

 Fisher, Parmelee, Heaton and Bartlett. The discussion of the same sub- 

 ject is to be continued at the next meeting. Adjourned to Thursday even- 

 ing, March 3 1st. 



American Institute Polytechnic Association, ) 

 3Iarch 31, 1864. ) 

 Chairman, Prof. S. D. Tillman; Secretary, Mr. B. Garvey. 

 The fuUowing interesting summary of scientific intelligence was pre- 

 sented by the Chairman : 



