s called a quoin, and keeps
the bolster in its place. The figure 9 represents one of the many bolts
by which the whole is kept in place on the boat.

[Illustration: A MORTAR.]

The boat is built like a raft, of thick timbers, laid crosswise and
bolted firmly together. It is about thirty feet long and twelve wide,
and has iron plates around its sides to screen the men from Rebel
sharpshooters. The mortar is more than four feet in diameter. It is
thicker than it is long. To fire a mortar accurately requires a good
knowledge of mathematics, of the relations of curves to straight lines,
for the shell is fired into the air at an angle of thirty or forty
degrees. The gunner must calculate the distance from the mortar to the
enemy in a straight line, and then elevate or lower the muzzle to drop
his shell not too near, neither too far away. He must calculate the time
it will take for the shell to describe the curve through the air. Then
he must make his fuses of the right length to have the shell explode at
the proper time, either high in the air, that its fragments may rain
down on the encampment of the enemy, or close down to the ground among
the men working the guns. It requires skill and a great deal of practice
to do all this.

The mortar flotilla was commanded by Captain Henry E. Maynadier,
assisted by Captain E. B. Pike of the engineers. There were four Masters
of Ordnance, who commanded each four mortars. Each mortar-boat had a
crew of fifteen men; three of them were Mississippi flatboatmen, who
understood all about the river, the currents and the sand-bars.

Commodore Foote's flotilla consisted of the Benton, 16 guns, which was
his flag-ship, covered all over with iron plates, and commanded by
Captain Phelps; the Mound City, 13 guns, commanded by Captain Kelty; the
Carondelet, 13 guns, Lieutenant Walke; the Cincinnati, 13 guns, Captain
Stemble; the St. Louis, 13 guns, Captain Dove; the Louisville, 13 guns,
Lieutenant Paulding; the Pittsburg, 13 guns, Lieutenant Thompson; the
Conestoga, 9 guns, Lieutenant Blodgett; in all, 103 guns and 10 mortars.
The Conestoga was used to guard the ammunition-boats, and took no part
in the active operations. Commodore Foote had several small steam-tugs,
which were used as tenders, to carry orders from boat to boat.

The Southern people thought that Island No. 10 could not be taken. On
the 6th of March a newspaper at Memphis said:--

"For the enemy to get possession of Memphis