PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 515 



half an hour. The Ironsides not having- the same thickness of plates as the 

 monitors coukl 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 weak- 

 nesses 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 Port 

 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 con- 

 structed 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 velo- 

 city alone; this is shown in firing a soft metal through a hard one, such as a 

 leaden 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 ob- 

 structions in the entrance to harbors, and one which, if we fully avail our- 

 selves 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 htmdred yards, and none of the hvdls are known thus far to be pene- 

 trated or a single ball to go through the turrets, nor a man on board to 

 have lost Ms life. These are very important points to reflect upon; a con- 

 test of 300 guns against 14 is indeed veiy 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 destro^y 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 



