In the same magazine as the Stonewall Jackson article there was an article in regard to the history of the Mortar. From the earliest known "forerunner to the mortar introduced by the Spanish Muslims in about AD 1250," to the modern day, the article reviews the value of the mortar as a piece of artillery, it's uses, and improvements over the centuries, as well as the development of the mortar as a valued instrument of war.
The mortar provided besiegers of cities a means for lobbing missiles down upon entrenched troops and positions forward of the main target as well as over city walls. In at least one example the besieged Knights Hospitallers of the Order of St. John used mortars to drop 100 lb. stones and other missiles upon the Turk's artillery emplacements on the island of Rhodes in 1480.
Mortar ships were developed in the 17th century and were very handy in putting munitions / missiles into forts on high bluffs coming close enough to the land to avoid the major ordnance of any given fortification. Advances in the 19th century gave rise to the Coehorn Mortar and the use of larger mortars in the Civil War and in mortar pits for fortification development in the latter part of the century. Today the mounting of mortars for rapid field deployment is a tactical necessity.
Pictures of some mortars and their usage will follow.
Reference:--William McPeak, "The Mortar Is Perhaps---," Military Heritage Magazine, Col. Weapons, Sovereign Media, Herdon, Va. Pages 12-15.