The following is from the Putnam's The Rebellion Record: A Diary of American Events, Vol 4, (1862) on pages 279-280. 

Who Planned the Merrimac?

RICHMOND, March 29th, 1862.

Hon. Thomas S. Bocock, Speaker of the House of Representatives:

SIR: In compliance with the resolution adopted by the House of Representatives, on the eighteenth inst., "That the Secretary of the Navy be requested to make a report to this House of the plan and construction of the Virginia, so far as the same can be properly communicated; of the reasons for applying the plan to the Merrimac; and, also, what persons have rendered especial aid in designing and building the ship," I have the honor to reply, that on the tenth day of June, 1861, Lieut. John M. Brooke, confederate States navy, was directed to aid the Department in designing an iron-clad war-vessel, and framing the necessary specifications.

He entered upon this duty at once, and a few days thereafter submitted to the department, as the result of his investigations, rough drawings of a casemated vessel with submerged ends and inclined iron-plated sides. The ends of the vessel, and the eaves of the casemate, according to his plan, were to be submerged two feet; and a light bulwark, or false bow, was designed to divided the water, and prevent it from banking up on the forward part of the shield with the vessel in motion, and also to serve as a tank, to regulate the ship's draft. His design was approved by the department, and a practical mechanic was brought from Norfolk to aid in preparing the drawings and specifications.

This mechanic aided in the statement of details of timber, etc., but was unable to make the drawings; and the department then ordered Chief-Engineer Williamson, and Constructor Porter, from the navy-yard at Norfolk, to Richmond, about the twenty-third of June, for consultation on the same subject generally, and to aid in the work.

Constructor Porter brought and submitted the model of a flat-bottomed, light-draft propeller, casemated battery, with inclined iron-covered sides and ends, which is deposited in the department. Mr. Porter and Lieut. Brooke have adopted for their casemate a thickness of wood an iron and an angle of inclination nearly identical. Mr. Williamson and Mr. Porter approved of the plan of having submerged ends to obtain the requisite flotation and invulnerability, and the department adopted the design, and a clean drawing was prepared by Mr. Porter of Lieutenant Brooke's plan, which that officer then filed with the department. The steam-frigate Merrimac had been burned and sunk, and her engine greatly damaged by the enemy; and the department directed Mr. Williamson, Lieut. Brooke, and Mr. Porter to consider and report upon the best mode of making her useful. The result of their investigations was their recommendation of the submerged ends, and the inclined casements for this vessel, which was adopted by the department.

The following is the report upon the Merrimac:

"In obedience to your order, we have carefully examined and considered the various plans and propositions for constructing a shot-proof steam battery, and respectfully report that, in our opinion, the steam-frigate Merrimac, which is in such condition from the effects of fire, as to be useless for any other purpose, without incurring a very heavy expense in her rebuilding, etc., can be made an efficient vessel of that character, mounting .  .  .  heavy guns, and from the further consideration that we cannot procure a suitable engine and boilers for any other vessel, without building them, which would occupy too much time, it would appear that this is our only chance to get a suitable vessel in a short time. The bottom of the hull, boilers, and heavy and costly parts of the engine being but little injured, reduces the cost of construction to about one-third of the amount which would be required to construct such a vessel anew.

Immediately upon the adoption of the plan, Porter was directed to proceed with the constructor's duties. Mr. Williamson was charged with the engineer's department; and to Mr. Brooke was assigned the duties of attending to and preparing the iron and forwarding it from the Tredegar Works, the experiments necessary to test the plates, and to determine their thickness, and devising heavy rifled ordnance for the ship, with other details pertaining to ordnance. Mr. Porter cut the ship down, submerged her ends, performed all the duties of constructor, and originated all the interior arrangements by which space has been economized, and he has exhibited energy, ability, and ingenuity. Mr. Willliamson thoroughly overhauled her engines, supplied deficiencies, and repaired defects, and improved greatly the motive power of the vessel.

Mr. Brooke attended daily to the iron, constructed targets, ascertained by actual tests, the resistance offered by inclined planes of iron to heavy ordnance, and determined interesting and important facts in connection therewith, and which were of great importance in the construction of the ship; devised and prepared the models and drawings of the ship's heavy ordnance, being guns of a class never before made, and of extraordinary power and strength.

It is deemed inexpedient to state the angle of inclination, the character of the plates upon the ship, the manner of preparing them, or the number, calibre, and weight of the guns; and many novel and interesting features of her construction, which were experimentally determined, are necessarily omitted.

The novel plan of submerging the ends of the ship and the eaves of the casemate, however, is the peculiar and distinctive feature of the Virginia. It was never before adopted. The resistance of iron plates to heavy ordnance, whether presented in vertical planes or at low angles of inclination, had been investigated in England before the Virginia was commenced; and Major Barnard, U.S.A., had referred to the subject in his "Sea-Coast Defences."

We were without accurate data, however, and were compelled to determine the inclination of the plates and their thickness and form, by actual experiment.

The department has freely consulted the three excellent officers referred to, throughout the labors on the Virginia, and they have all exhibited signal ability, energy, and zeal.

I have the honor to be, very respectfully,
                    Your ob't servant.
                               S. R. MALLORY,
                                     Secretary of the Navy.

CSS Virginia
Transcription copyright 1997 by Martha H. Tyson and Mabry Tyson