494 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



armor, but we propose to apply it in alternate layers with iron plates' 

 When used in this manner, we have found that the balls have more work 

 to do. The iron reacts and the base of resistance is enlarged around the 

 point of impact, consequently diffuses the force of the blow over a greater ex- 

 tent of surface. This has been practically demonstrated on some of our gun- 

 boats on the Mississippi river, as well as by firing at a target, a few days since» 

 in Washington city, — a target composed of four one-inch plates of iron 

 alternately arranged with four one-inch plates of vulcanized India rubber. 

 These plates were ninety-six inches long by forty-two wide; they were 

 bolted to a block of oak twenty inches thick, with six bolts one and a half 

 inches in diameter. The bolts were provided with elastic washers four 

 inches in diameter and three inches thick. This target was placed against 

 a perpendicular bank of clay, or as civil engineers would call it, " hard- 

 pan," range twenty-five steps, or say seventy-five feet, at right angles with 

 the muzzle of an eleven-inch Dahlgren gun, and fired at with a charge of 

 thirty pounds of fine grain powder and a solid shot. Of course it was pene- 

 trated under such circumstances, but it broke the shot into pieces. I hold 

 in my hand a piece of the shot. The hole in the surface or outside plate 

 measured eleven and a quarter inches; in the second, the plug or piece 

 punched out measured thirteen and a half inches in diameter; in the third, 

 fifteen inches in diameter, and in the fourth, seventeen inches over the con- 

 cave surface. 



To get comparative results, a target of a similar size, composed of four 

 one-inch iron plates, bolted to a similar block with ten screw bolts, set up in 

 the same manner and of the same range, was also penetrated by a solid 

 shot with the same change and gun. The holes in the four plates on this 

 target were each a fraction less than twelve inches — for comparison I will 

 calculate them at twelve inches — number of square inches in the four plugs 

 punched out of my target equal 815 square inches; to square the diameter 

 of the holes in the all iron target, we find them equal 576 square inches, — 

 difference 239 square inches. To this must be added the number of square 

 inches that would be equal to the force required to compress the rubber, 

 and then we shall have the means of comparison. I am not very precise 

 you will see. My reasons are, that the Assistant Secretary of the Navy, 

 Mr. Fox, told me they would be published, and I did not collect all the 

 details. 



A target composed of a 4| inch solid plate, screwed to a similar block 

 of wood, was also fired at with an eleven inch solid shot. This plate was 

 badly broken, as you will see from the diagram, and here is a piece of each 

 target; also some of the India rubber. 



Having given you the details of the effect of an eleven inch shot striking 

 plate armor at seventy-five feet, arranged according to the plan we pro- 

 posed, but set against a clay bank, I will state that whenever we have 

 fired at two inches thickness of iron and one of rubber, backed by two feet 

 of oak, inclined at an angle of forty-five degrees, the shots have been 

 either deflected or rebounded, as I will show you by affidavits of the 

 gentlemen that were on board the gunboat Choctaw. I will also state 

 that my target at Washington city, was not put up in the manner and at 



