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The Yankee Iron-Clad Navy--Admiral Dahlgren's opinion of monitors.

We have before us a copy of Rear Admiral Dahlgren's report to the Secretary of the Navy, of the services of the monitors before Charleston. The concluding portions of the report are of a general character as to the services and capabilities of the monitors, which we give in full. The accompanying report is from Commodore John Rodgers, who has had more experience with monitors in actual warfare than any other officer of the navy:

After conflicts.

The operations of the iron-clads against Morris Island were appropriately closed by a severe contest with Fort Moultrie, Batteries Bee, Beauregard, &c., to relieve the Weehawken, which had grounded under their fire, and was finally got off with some severe injuries, owing to the falling tide having exposed the hull under the overhang.

There were other occasions when severe conflicts occurred with the rebel works on Sullivan's Island. And besides the principal attacks in force there were few days from the first attack (July 10th) to its evacuation (September 7th ) that some Iron-clads or gunboats were not engaged in firing at the enemy's works, so as to facilitate the labor of our troops ashore, as will be perceived by the following sample from the record:

Date --1863ObjectVess's engaged.
July 18assault on WagnerMontank, Flag, Kaats kill, Nantucket, Weehauken, Patapson; gunboats Paul Janes, Ottawa, Seneca, Chippewa, Wissahickin
July 22WagnerNantucket, Ottawa, (gunboat)
July 24Wagner to cover advanceWeehauken, Flag, Ironsides, Kaatskill, Montauk, Patapsco, Nantucket.
July 25WagnerG'bts Paul Jones, Seneca, Ottawa, Daiching.
July 28WagnerGunb'ts Ottawa, Dalching, Paul Jones
July 29WagnerWeehauken., Kaats kill, Ottawa, (gbt)
July 30WagnerIronsides, Patapsco,
July 31rebel batteries on Morris IslandIronsides, Kaatskill, Patapsco, Ottawa, (gunboat.)
August 1WagnerOttawa, (gbt)
August 2WagnerMontauk, Kaatskill, Patapsco, Weehauken, Nahant, Passic, Marblehead, (gunboat.)
August 4WagnerMarblehead, Ottawa, (gunboats,)
August 6WagnerMontank, Marblehead, (gunboat.)
August 8WagnerMarblehead, (gbt)
August 11Wagner and vicinityOttawa, Marblehead, Mahaska, (Gbts.)
August 13rebel batteries on Morris IslandPatapsco, Kaatskill
August 14rebel batteries on Morris IslandGunb'ts Dal Ching, Ottawa, Mahaska, Wissahickin, Racer
August 15Wagnergunboats Wissahickin, Mahaska, Ottawa, Dal Ching, Racer, Dan Smith.
August 17rebel bat'rs on Morris Island to divert fire from our batteries, which opened on SumterMortar boats Racer, Dan Smith.
August 18Wagner to prevent assaultWeehauken, Iron sides, Montauk, Nahant, Passaic, Kaatskill, Patapsco; gunboats Canandalgua Mahaska, Ottawa, Cimerone, Wissa hickin, Dal Ching Ladona.
August 19WagnerIron sides, Passaic, Weehauken, gunboats Wissahickin, Mahaska, Dal Ching, Ladona, Ottawa.
August 20rebel batteries on Morris IslandIronsides.
August 21Sumter and WagnerIronsides, gunboats Mahaska, Ottawa, Ladona, Dal Ching.
August 22WagnerIronsides, Patapsco, gunboats Mahaska, Dal Ching
August 23SumterWeehauken, Ironsides, gbt Montauk
September 1SumterWeehauken, Passaic, Patapsco, Montauk, Nahant.
September 5Obstructions bet'n Sumter and GregWeehauken, Nahant, Patapsco. Montauk, Passaic, Lehigh.
September 6Wagner and GreggLehigh, Nahant.
September 7Batt'rs on Sullivan's Isl'd.Ironsides, Wechauken, Montauk, Passaic, Patapsco, Nahantt, Lehigh
September 8Batt'rs on Sullivan's Isl'd.Ironsides, Patapsco, Lehigh, Nahant, Montauk, and Weehauken, (ashore.)

I shall now briefly comment on the various qualities of the monitors:

  1. 1. Capacity for resistance.
  2. 2. power of ordnance.
  3. 3. draft of water.
  4. 4. speed.
  5. 5. number of crew.
I. Endurance.--During the operations against Morris Island, the nine Iron-clads fired eight thousand projectiles, and received eight hundred and eighty-two hits. Including the service at Sumter in April, and the Ogechee, the total number was eleven hundred and ninety-four, distributed as follows:

Service of the Iron-clads.

number of Shots Fired 15 inchnumber of Shots Fired 11-inch.HitsHits April 7th, 1863Hits at Ogecheetotal Hits

No, shots fired.Weight projectiles fired in tons.
By Ironsides 4439228½
11-inch by Monitors 2332 3587151½ 365
15-inch by Monitors 1255 3587213½ 365

Of the eight monitors, one was always absent at Warsaw (Nahant or Nantucket) to blockade the rebel ram.

The Lehigh did not arrive until August 30th, therefore was only able to participate in the operations of the remaining seven days, but did good work.

For some time only five monitors were available for general attack, and then six, which was the greatest number disposable at any one time. The consequence of the protracted bring and hard usage to which the monitors were exposed during these two months of incessant service, were unavoidably very considerable in the aggregate; and the greater also that all repair which could possibly be dispensed with was postponed to the conclusion.

It was, therefore, necessarily extensive when entered upon. The battering received was without precedent. The Montauk had been struck two hundred and fourteen (214) the Weehawken one hundred and eighty-seven (187) times, and almost entirely by 10-inch shot.

What vessels have ever been subjected to such a test?

It is not surprising that they should used considerable repair after sustaining such a severe pounding for so long a time, but only that they could be restored at all to a serviceable condition. The force of a 10-inch shot must be experienced to be appreciated. Any one in contact with the part of the turret struck falls senseless, and I have been nearly shaken off my feet in the pilot house when engaging Moultrie.

All the little defects of detail were marked by such a searching process Decks were cut through; cannon were rooted out; side armor shaken; tops of pilot-houses crushed, &c, But all these were reparable, and no vital principle was seriously touched With such workshops and means as a Northern Navy Yard includes, the repair of all monitors would have been speedily executed; but when machinery, tools, labor and material have all to be obtained, as they were here from a great distance, there was of necessity considerable delays; and moreover, it was not admissible to withdraw but a portion of the Monitors at a time from the blockade.

The additions that were deemed advisable for strengthening the pilot-houses and turrets were also put on at this time, and the bottom cleaned, for they had now become so foul with oysters and grass, that the speed was reduced to three or three and a half knots, and with the strong tide of this labor, added considerably to the difficulties of working the vessels properly under fire.

One night I was caught by heavy weather from southeast, while close up to Sumter, when I had gone to attack it, and it was well that the darkness of the night prevented the slowness of our motion being perceived, while extricating the monitors from their position.

Power of ordnance.

Each turret contains two guns, and from the peculiar facility which it has for giving direction to the heaviest ordnance, no doubt arises the desire to make these of the heaviest description. How far other considerations should control the character of the ordnance, is necessarily an unsettled question.

To strike an armored ship, it may be best to use a gun capable of the greatest power; but whether this shall be derived from a projectile of great weight, driven by low velocity, or of less weight and high velocity; whether it shall be a 15-inch gun, fired with thirty five or forty pounds, or a 13 inch, fired with fifty pounds of powder, is not here material; the weight of the gun for either purpose will not vary to any important degree. But in operations against earthworks, whose material cannot be damaged permanently, but only disturbed, and which are only to be dealt with by keeping down their fire, a much lighter projectile would be preferable, in order that the practice may be as rapid as possible. Hence a piece of 16,000 lbs for 10 inch or 11 inch shot and shell.

When a number of monitors are brought together, it would be better also to have guns of like kind in each turret, and bringing into action which ever might be preferable.

Each of the monitors of this squadron had a 15 inch and a smaller gun, 11 inch or 8 inch rifle, and hence the rapidity of fire which was most desirable was not attained. That this was due to the calibre of the gun, and not to its being located in a turret may be shown by one notable instance.

November 9, 1863, the Montank, Capt Davis, was engaged in battering Sumter. In so doing, the 11-inch gun fired twenty five shells successively in one hour, of which twenty one hit the wall of the fort aimed at — distance sixteen hundred yards. This is at the rate of one shell in 24 minutes, which is not only rapid, but also exceedingly accurate practice.

There is no reason why another 11 inch, if placed in the adjoining carriage, instead of the 15 inch, could not have been fired in the same time, at which rate that monitor would have delivered an 11-inch shell every 12 minutes.

The rates of fire reported for the Ironsides by Capt Rowan are:

Time. Hours — Minutes.No. Fired.Time for each fire. Minutes.
Most rapid 0.05251.74
Continuous 2.554902.86
Assumed 1.003601.33
Montauk 1.00252.40

It will be perceived that for a short space of time the frigate delivered a shell from each gun in 1.74 minutes for three hours in 2.86 minutes; and it is believed that a fire could be sustained at the rate of 7.33 minutes. The last rate is, therefore, possible; but I am sure it would be difficult to sustain it long with much regard to good aim and considerable distances; and I believe, on the whole, that for every practical purpose there would be all desirable rapidity of fire from the 11 inch turret.

Thus it is to be presumed that there will be equality of advance power in the same number of 11 inch guns as to the rapidity of fire whether in a turret or broadside.

Draft of water.

The monitors of the Passaic class draw about 11½ feet of water when properly trimmed. On this coast 10 and 11 feet is the most convenient draft of water for penetrating all the principal sounds and rivers, and navigating them to any extent. A greater draft restricts a vessel in movement, and in many instances excludes her from several ports, except under very favorable circumstances.


The speed of the monitors is not great, (seven knots,) but it is quite respectable with a clear bottom, and is fully equal to that of the Ironsides.--Their steerage is peculiar, but, when fully understood and rightfully managed, not difficult of control. They pivot with celerity, and in less space than almost any other class of vessels.

Number of men.

The number of men required to work them and the guns is only eighty, which is very moderate. --In common with all iron clads, the scope of vision is much restricted, for the plain reason that in such vessels apertures of any size must be avoided.--There are some other defects, but they are not in horrent and, it is believed, are susceptible of being remedied wholly or in part. So much for the monitors.

The Ironsides.

The Ironsides is a fine powerful ship. Her armor has stood heavy battering very well, and her broadside of seven 11-inch guns, and one 8-inch rifle has always told with signal effect when opened on the enemy. Draft of water about 15½ to 16 feet--Speed 6 to 7 knots, and crew about four hundred and forty men.

The defects of the vessel are the unplated ends, which are consequently easily damaged by a raking fire, and involve the rudder and screw more or less, while she can return no fire in either direction. This was particularly and frequently inconvenient in attacking the works on Morris Island, for at certain stages of the tide vessels tall nearly across the channel, and present bow and stern to the beach of Morris Island. So that sometimes it was necessary to delay placing the vessels in position, and at others she would swing around very awkwardly when engaged.

The monitors, on the other hand, were almost equally well defended on all sides, and could fire in any direction. The Ironsides was also open to descending shot, and her scope of fire too much restricted by badly placed ports. The desire for comparison which rages just now can easily be satisfied by bringing the above data in juxtaposition. Just as they are, the Ironsides is capable of a more rapid and concentrated fire, which, under the circumstances, make her guns more effective than the 15 inch of the monitors.

On the other hand, she was restricted by draft to the mid-channel, was very vulnerable to the raking fire, and the direction of her own guns was very limited interally. The monitors could operate in most of the channels, could direct their fire around the whole circle, and were almost equally well defended on all sides. The defects in both classes of vessels are susceptible of being remedied partially or entirely. The defence of the Ironsides could be made complete, and that of the monitors equally so. The armament of the monitors equally could be perfected so as to give all desirable rapidity of fire, but by no contrivance could the Ironsides be enabled to use much heavier guns than those mounted. Yet when such changes were made as experience suggested, there still would remain to the monitors the lighter draft, choice of guns from the heaviest to the lightest, defensibility, and direction of fire around the whole circle; consequently the ability to carry a heavier battery into the least depth of water, with equal power of offence and defence in any direction, and that with half the number of guns carried in broadside by another vessel.

Comparison of Iron-clads.

The comparison now made is to be understood as having relation to existing circumstances, and not at all intended as conclusive in regard to the general merits of iron-clads.

It is in this sense that the action of the Navy Department is to be considered with reference to the selection of one class of vessels over another.

It is evident that it was not designed to adopt any one style exclusively, for of the three vessels first ordered, two were of the ordinary broadside class — the Ironsides and the Galena. The latter was quickly proved to be absolutely inefficient, and so must any armored steamer of that size. It is universally admitted that plates of less than four and a half (4 ½) inches cannot stand the shock of heavy projectiles, and vessels so armored must be of considerable tonnage. I presume the Department only intended to build such vessels as were best adapted to the service at the scene of war.

Keeping in view the peculiar exigencies of the case, which required light draft and great ordnance power, it appears that the selection of the Department could not have been more judicious in preferring a number of monitors to operate from a heavy frigate as a base; and of the intent of the Department could have been carried out in regard to numbers, we should now have been in entire possession of the coast from the Capes of Virginia to New Orleans, including Wilmington, Charleston, Mobile, &c.

Many detects of both classes are easily remediable, but some of those in the monitors could only be determined by the lost of battle; before that, approximation only was possible.

What other style of vessel could the Department have chosen? Certainly none that has been built by English or French naval authorities. The Warrior and her class are exceedingly powerful, but could not get within gunshot here. On the other hand, there is very little navigable water on the coast which is not accessible to the monitors. They command supremely all that is near the shore, and cannot themselves be reached by vessels of heavier draft. So that when there was some reason to apprehend the appearance of certain rams in this quarter, I assured the Department that the iron-clads could maintain position so long as coal and provisions lasted.

It may appear that I speak too positively on the subject, but some experience with them certainly gives a right to do so.

With a single exception, I have been on board a monitor in all the principal actions, and the recurrence of casualties to the Fleet Captains near me shows that I was in a situation to judge. I was once in the Ironsides in at attack on Moultrie and Sumter. I have also watched the behavior of the monitors at anchor through all the phases of winter weather in this exposed situation.

The completeness with which four little monitors, supported by an iron-clad frigate, have closed this nothing. Very soon after entering the Roads, I advanced one monitor well up towards the inner debouches of the Northern Channel, supported by another. On the night of the 19th of July, an English steamer attempted to run in, and having eluded the hot pursuit of the outside blockade, no doubt indulged in the belief that all danger was past. But the gallant Captain Rodgers was in advance that night with the Kaatskill, and a shell sent suddenly by him ahead of the culprit steamer signified he escape. In despair or alarm the latter grounded on a shoal, and her wreck has since served as a warning to like evil doers. Two or three steamers that were in, managed to get out immediately after, and one or two may have gotten in, for the crews of the monitors were often too fatigued then with a day's battle to keep watch at night; but there ended the business as such, and for several months not a vessel has passed in or out.

These four monitors, who thus keep watch and ward, muster eight (8) guns and three hundred and twenty (320) men, which is almost insignificant in contract with the work done.

I have thus put on paper the general impressions now uppermost, but very hastily and under great pressure of business, which will; I hope, excuse such imperfections as may have inadvertently occurred. With more leisure I could do full justice to this interesting subject.

I have the honor to be, &c.

John A. Dahlgren, Rear Admiral,
Commanding S. A. B. S.
Hon. Gidson Weles, Secretary of the Navy.

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