tugged away with devil's-claw and
slice-bar, inducing by their exertions more and more intense combustion
and heat. The noise of the cracking, roaring fires, escaping steam, and
the loud and labored pulsations of the engines, together with the roar
of battle above and the thud and vibration of the huge masses of iron
which were hurled against us produced a scene and sound to be compared
only with the poet's picture of the lower regions.

And then an accident occurred that threatened our utter destruction. We
stuck fast aground on a sand-bar.

Our situation was critical. The _Monitor_ could, at her leisure, come
close up to us and yet be out of our reach, owing to our inability to
deflect our guns. In she came and began to sound every chink in our
armor--every one but that which was actually vulnerable, had she known
it.

The coal consumption of the two days' fight had lightened our prow until
our unprotected submerged deck was almost awash. The armor on our sides
below the water-line had been extended but about three feet, owing to
our hasty departure before the work was finished. Lightened as we were,
these exposed portions rendered us no longer an ironclad, and the
_Monitor_ might have pierced us between wind and water had she depressed
her guns.

Fearing that she might discover our vulnerable "heel of Achilles" we had
to take all chances. We lashed down the safety valves, heaped
quick-burning combustibles into the already raging fires, and brought
the boilers to a pressure that would have been unsafe under ordinary
circumstances. The propeller churned the mud and water furiously, but
the ship did not stir. We piled on oiled cotton waste, splints of wood,
anything that would burn faster than coal. It seemed impossible that the
boilers could stand the pressure we were crowding upon them. Just as we
were beginning to despair there was a perceptible movement, and the
_Merrimac_ slowly dragged herself off the shoal by main strength. We
were saved.

Before our adversary saw that we were again afloat we made a dash for
her, catching her quite unprepared, and tried to ram her, but our
commander was dubious about the result of a collision without our
iron-shod beak, and gave the signal to reverse the engines long before
we reached the _Monitor_. As a result I did not feel the slightest shock
down in the engine-room, though we struck her fairly enough.

The carpenter reported that the effect was to spring a leak forward