"And no other vessel was built that way by the Confederate States. Subsequent vessels were made after the model which Constructor Porter made at Pittsburg in 1847, with the ends above the water and protected like the roof."
But the model made after the return of the ship-carpenter to the yard, like the one he made at Pittsburg, had its ends under the roof and submerged "just two feet," and no vessels were ever built after that model in the Confederate States.
When the Merrimac, after conversion, was floated, it was found that in consequence of an error in her computed displacement her ends and eaves could not be submerged to the depth proposed. This was a serious matter, as the additional weights required to bring her down involved an otherwise unnecessary increase of draft. Constructor Porter says in his Century note:
"Her deck ends were two feet below water and not awash, and the ship was as strong and well protected at the centre line as anywhere else, as her knuckle was two feet below her water-line, and was then clamped."
The following letters state the facts:
"'VIRGINIA,' NORFOLK YARD, March 5, '62.
."*** I hope we will get off on Thursday night. The ship will be too light, or, I should say, she is not sufficiently protected below the water. Our draft will be a foot less than was first intended, yet I was this morning ordered not to put any more ballast in fear of the bottom. The eaves of the roof will not be more than six inches immersed, which in smooth water would not be enough; a slight ripple would leave it bare except the one-inch iron that extends some feet below. We are least protected where we most need it, and may receive a shot that would sink us; a thirty-two-pounder would do it. The constructor should have put on six inches where we now have one.
"We have taken on board a large quantity of ballast.
"CATESBY AP. R. JONES."