516 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



twenty-four hours, and thf^se obstructions can be removed in less than two 

 weeks; but in making these obstructions, there should be openings made 

 at certain places, to which floating gates should be attached, that could be 

 removed whenever it was necessary for vessels to pass in and out. But in 

 addition to these obstructions for harbor defence, we should have rams 

 capable of going twenty-five miles an hour, to go outside and engage the 

 enemy there. 



Mr. Bartlett. — The best form of shot, and that which will give the 

 greatest penetration, has been fully experimented upon by Mr. Lyman. 

 The best form he has found to be that which is called the cylindrico con- 

 oidal, or a piece cut off the front end of a cylindrical bolt; these balls 

 have been found very effective in punching. 



The Chairman. — In some late experiments, I see it stated that it does 

 not make much difference as to the shape of the ball, as several different 

 shaped shot appeared to have the same penetrating power. 



Mr. Dibben.— The shape of the shot is not material; it depends entirely 

 on the velocity for its punching effect; but the mere piercing of plates with 

 a very small shot will not disable a ship very much. There are no guns 

 in the service^known to be better than the Pari'ottguns, and these, and the 

 Whitworth gun, have done more than any other in the way of heavy pene- 

 tration. 



Mr. Bartlett. — It is well understood that deep penetration is the result 

 of velocity; but Mr. Lyman's son told me that he tried several kinds of 

 shot with the same charge of powder, and found the form I have mentioned 

 to be the best. 



Prof. Everett. — A hollow cylinder open at one end, on the principle of 

 the apple peeler, has penetrated through four-inch iron plates at 150 feet 

 distance. 



Dr. Stevens. — While we are speakng of iron-clads, and comparing their 

 efficienc}' on the southern waters, we should not forget that the Mississippi 

 river was plowed by a gunboat clad with only an inch in thickness of 

 iron, and one inch of India rubber, and I think that our present iron-clad 

 vessels could hardly have endured as much. Pure India rubber was found 

 to be too elastic, and they combined fibrous material with it. Commodore 

 Porter said, when in this city, that when the Essex was struck with a shot, 

 it sounded like a large drum. The Essex was only iron-clad in front, and 

 took part in all the heavy work going on. She took part at Forts Henry 

 and Donelson where she received a shot through her chimney; and when 

 at Island No. 10, she had workmen put on board, who fitted her up as she 

 went along, and repaired damages after an engagement. She destroyed 

 the Arkansas, which was clad with the T rail, and she made these rails 

 fly very fast. The question is why other vessels like her were not built; 

 this question has not, to my knowledge, ever been answered. But I know 

 that when the rebels drove piles in the sand, to obstruct the progress of 

 Gen. Pi-entissin North Carolina, and when a council was held, the Gene- 

 ral said to the engineer, in the presence of the negro pilot that "the 

 Almighty himself could not remove those obstructions." The engineer and 

 negro pilot went that evening and took soundings, and the next night 

 they entirely reraoyecl those obstructions, and the negro said that the 



