600 TRANSACTIONS OP THE AMERICAN INSTITUTE. 



but that ail the shots fired would have been as successfully resisted as was 

 the first one mentioned in the second experiment. 



The true value of this, or any other plan, can never be fully determined 

 by men who will employ thick iron and gutta-percha as a substitute for 

 thinner plates and Indiarubber. The difference in the cohesion of the fibres 

 of thick plates, and those of thin ones, was fully determined at the Laclede 

 Iron Works, in St. Louis, on plates two and a half inches in thickness and 

 plates one inch thick; both being made from similar stock, and underwent 

 the usual manipulations due to the manufacturing of plates of similar thick- 

 ness. Each plate had the outside fibres cut with a chisel, and was then 

 put under a trip-hammer and subjected to a bending operation. The two 

 and a half inch plates broke with the first stroke of the hammer; it requir- 

 ed several blows to break the one-inch plates, as they would bend back 

 and forth before breaking. 



Aside from the beforementioned experiment, there are other important 

 reasons why iron should be applied to the sides of a vessel in separate 

 plates, more effectually to oppose resistance to penetration. 



Fiist. It is well known that thick plates of iron cannot be forged or roll- 

 ed of the proportionate strength of thin plates, for the reason that the 

 former are liable to become granulated in the operation, more full of flaws, 

 and not of so homogeneous a texture as thin plates. 



Second. It is also well known that two surfaces of iron offer greater re- 

 sistance to penetration than one, because the surface of each plate, to the 

 depth of one-sixteenth or one-eighth of an inch, is much harder and tougher 

 than the interior. 



Third. The joints can be broken by separating the plates. 



Fourth. By the interposition of the India rubber plates, Space is afforded 

 to interlock and strongly connect the iron plates with each other, by means 

 of flanges and grooves, which not only enlarges the base of resistance to 

 shot, but adds strength to the sides of a ship. 



Fifth. When the iron plates are thus interlocked and connected together, 

 less thickness of timber is required to sustain them. 



Sixth. When all the iron plates are strongly connected, so as to support 

 each other, and the sides of the ship, the iron plates cannot act as a dead 

 weight, and tend to tear asunder the sides of a vessel longitudinally, as 

 has been found to be the case wiien the iron plates are not so connected. 



In conclusion, you are herewith furnished with the relative capacity of 

 oak and iron to resist penetration; also with the specific gravity of the ma- 

 terials herein under consideration. 



It has been shown, by experiments, that one inch of good tough wrought 

 iron would oppose about as much resistance as thirty inches of partially 

 seasoned oak. 



The specific gravity of such a plate of iron is *I.T88, and its weight forty 

 pounds per superficial foot. 



The specific gravity of James river oak, wheyi well seasoned, \s 0.159, and 

 will average in weight sixty pounds per cubic foot; the same may be said 

 of western burr oak. 



The specific gravity of India rubber is 0.933, and when manufactured 

 into plates, as proposed, will weigh about eight pounds per superficial foot- 



