Meantime rifled cannon made of cast iron reinforced over the breech by a wrought-iron jacket that was shrunk on had been introduced into the American navy. They varied from thirty-pounders up to 100-pounders, and, except for the smaller calibres, were in many cases more dangerous for their crews than for the enemy. It must be told also that a cast-iron rifle known as the Brooke, because designed by Commander John M. Brooke, of the Confederate navy, was produced in Richmond that was better than the Parrott. It was strengthened in its early service days by a series of wrought-iron bands two inches thick and six wide, that were shrunk on over the breech. Later a second series of bands was shrunk on over the first, breaking joints with them, of course, and so a very good 150-pounder was produced. Meantime one Dahlgren smooth-bore, with a bore fifteen inches in diameter, had been successfully made, and the shells for all the Dahlgren guns were provided with fuzes that could be set to explode just about where and when the gunner wished to have them do so. But whether the damage to be done by a fifteen-inch round shot smashing its way through a ship’s side would be greater or less than that of a rifle projectile boring its way through was a question that had not been decided. It was granted that the rifle had the longer range--with a reasonable elevation a rifle would carry three miles, maybe four, and do some damage when the projectile arrived, while the effective range of the smooth-bore was, say, 1,500 or 1,600 yards, though gunners made efforts, when the time came, to run in to a range of 600 yards or less instead. But, on the whole, it was the belief among American naval officers before the Civil War that the big Dahlgren smooth-bore was the best gun afloat. [Illustration: Two Blakely Guns at the Brooklyn Navy Yard.] So it came to pass that the newest and best ships of the navy were armed with the Dahlgren gun. The _Merrimac_, which was not the best of the frigates, carried twenty-four nine-inch guns on her gun deck, with fourteen eight-inch and two ten-inch pivots on her spar deck. She could throw 864 pounds of metal from her gun-deck broadside, 360 pounds from her broadside of eight-inch guns, and 200 from her ten-inch, both of which could be fired over either rail.