The XIII inch bore Seacoast Mortar, Model of 1861 was a major factor in the force projection of the Federal military during the Unitd States Civil War. Its origin was in the British Royal Marine artillery as constructed for siege usage by Woolwich Arsenal in the 1850's. See James Atkinson Longridge for referance to the mind that created this period strategic weapon.

One XIII inch bore Mortar was at the head of the road leading off Eastney Esplanade into the Museum area of the Royal Marines. As of June 2006 the mortar had been removed from this position. It's current location is unknown. The inscription on the plaque was as follows:

CAST IRON SEA SERVICE 13-INCH MORTAR
(1855) USED FOR TRAINING PURPOSES BY
THE ROYAL MARINE ARTILLERY AT
EASTNEY

THIS TYPE OF MORTAR WAS DESIGNED TO
BE CARRIED ON A BOMB VESSEL AND USED
AS A BOMBARDMENT WEAPON. ITS RANGE
WAS 4000 YARDS (3700 METRES) AND THE
SHELLS POSSESSED GREAT PENETRATION
DUE TO THE HIGH ANGLE OF FIRE