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half an hour. The Ironsides not having the same thickness of plates as the monitors could not stand this battering. The monitors that were injured were made so by indentures made between the deck and the turrets, which prevented them from revolving; this was presumed to be one of the weaknesses of the monitors; but not a single Ericsson monitor was otherwise disabled in that fight, nor was there a gun disabled. I do not think a ship can be built to stand the fire of a 150 pound shot at an initial velocity of 1,400 or 1,500 feet in a second. We did not do serious injury to Fort Sumter, as might be supposed, as our shots had only some 800 or 900 feet velocity in a second. This speed will not do much damage to well constructed forts. None of the firing at Fort Sumter was capable of making a breach large enough to make two ports into one. Had this been done, there would have been some hope of continuing the attack; but the firing from our guns done no more than dent the walls some five feet. We have seen how much more effective is the rifle projectile than the round shot, which is due to its velocity, and indeed the whole question is one of velocity alone; this is shown in firing a soft metal through a hard one, such as a lea den ball through a copper cent; if the velocity is great enough, with a good gun loaded with nine or ten drachms of powder, and by throwing the cent in the air and when it is coming down by firing at it, the leaden ball will make a clean hole through it. Now, the secret of this is the speed at which the shot is fired; you can shoot at the cent all day with five drachms of powder without punching it. So it is with the large guns; the long rifle shot being two and three times the length of the diameter has a decided advantage in long range over the round shot, as one of three times the length of the diameter will have double the velocity of one of an equal diameter. The round shot is very effective for about two or three hundred yards, but beyond that the velocity decreases. A great many people have been disappointed in the late attack on Charleston; the obstructions seem to have been formidable enough to hinder our vessels entering the harbor. We have in it, however, an illustration of the perfect success of placing obstructions in the entrance to harbors, and one which, if we fully avail ourselves of, would compel an enemy to reduce Long Island before they could come up to this city, as it would be impossible for them to get to New York if they had to wait to remove these obstructions while the fire of our forts would be upon them. It was these obstructions only that prevented our monitors from entering Charleston. These seven monitors, carrying only fourteen guns, were exposed to a heavy fire at a distance of three to four hundred yards, and none of the hulls are known thus far to be penetrated or a single ball to go through the turrets, nor a man on board to have lost his life. These are very important points to reflect upon; a contest of 300 guns against 14 is indeed very remarkable, and that these seven monitors, with 14 guns, were able to stand the concentrated fire of 300 guns without any serious damage, is a most important event in naval warfare.

Dr. Stevens.-Would not these obstructions in the Narrows destroy the harbor and commerce of New York, for some time before they could be removed?

Mr. Dibben.-We can completely obstruct the harbor of New York in

twenty-four hours, and these 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 conoidal, 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 Parrott guns, 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 efficiency 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. Prentiss in North Carolina, and when a council was held, the General 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 removed those obstructions, and the negro said that the

engineer was greater than the Almighty and the General together. But that exploit finished the services of that engineer with Uncle Sam; he could not get any further employment in the service after that. Uncle Sam is always very considerate; he never undertakes any enterprise, without giving his enemy due notice, and he seems unwilling to undertake any movements until the advantages at least seem to be balanced on both sides.

Mr. Meissner.—I have made experiments in Washington with India rubber, and have seen a ball go through thick plates and thin ones. There was no trouble in piercing the India rubber one inch thick; we tried the pure rubber, and had it mixed with cloth. I had twelve balls pass through my target.

Mr. Bartlett.-I would like to know if there is any engineer's report of the doings of the Essex, and at what angle she was fired at? I have not the least doubt but that the inch plates of iron, and India rubber, can be easily penetrated.

Mr. Dibben.-From the position of the works which the Essex had to operate against, I am of the opinion that any one of the monitors would have stood more than six vessels of the Essex pattern. There is no difficulty in firing a ball through an inch of iron at an angle of forty-five degrees; the angle makes very little difference, unless there is a low velocity. These exploits of the Essex were confined to very poor forts; but at Charleston they had everything prepared, and they had the best English guns, which were served with precision and vigor. These guns were obtained through the blockade runners; and some of the guns taken from vessels trying to run the blockade and sent to this city, on the ends being cut off to make breech loaders, showed them to be of a very fine quality, and the ends looked like silver.

Dr. Stevens. All our gunboats are only an experiment, and the Essex was poorly adapted for one; she was nothing but a ferry boat run across the Mississippi, and built out west; she had to be put in fighting trim in a short time; she was under the batteries at Vicksburg for six hours; she destroyed several batteries below Vicksburg, and some of the shots received by the Essex were point blank. I think she has done more execution than all the others.

The Chairman.—It will be remembered that at Charleston our vessels had to stand the fire of five different forts at the same time, and at very short range. As to India rubber, it should be recollected that it is incompressible; that is, its atoms merely change their position by compression. Dr. Parmelee.—I should like to ask Mr. Meissner if the India rubber closed up after the ball passed through it?

Mr. Meissner. The shot made a large hole in the rubber, which immediately closed up again.

"The Manufacture of Sugar at the North," was selected as the subject for discussion at the next meeting.

Adjourned.

JOHN W. CHAMBERS, Secretary pro tem.

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