10-inch seacoast 5° 1,650
8-inch siege 12°30' 2,280
24-pounder naval 5° 1,270
12-pounder heavy naval 5° 1,085
20-pounder Dahlgren rifled 5° 1,960
12-pounder Dahlgren rifled 5° 1,770
[Illustration: Figure 36--ENGLISH MORTAR ON ELEVATING BED (1740).]
From earliest times the usefulness of the mortar as an arm of the
artillery has been clearly recognized. Up until the 1800's the weapon
was usually made of bronze, and many mortars had a fixed elevation of
45°, which in the sixteenth century was thought to be the proper
elevation for maximum range of any cannon. In the 1750's Müller
complained of the stupidity of English artillerists in continuing to
use fixed-elevation mortars, and the Spanish made a _mortero de
plancha_, or "plate" mortar (fig. 37), as late as 1788. Range for such
a fixed-elevation weapon was varied by using more or less powder, as
the case required. But the most useful mortar, of course, had
trunnions and adjustable elevation by means of quoins.
[Illustration: Figure 37--SPANISH 5-INCH BRONZE MORTAR (1788).]
The mortar was mounted on a "bed"--a pair of wooden cheeks held
together by transoms. Since a bed had no wheels, the piece was
transported on a mortar wagon or sling cart. In the battery, the
mortar was generally bedded upon a level wooden platform; aboard ship,
it was a revolving platform, so that the piece could be quickly aimed
right or left. The mortar's weight, plus the high angle of elevation,
kept it pretty well in place when it was fired, although English
artillerists took the additional precaution of lashing it down.
The mortar did not use a wad, because a wad prevented the fuze of the
shell from igniting. To the layman, it may seem strange that the shell
was never loaded with the fuze toward the powder charge of the gun.
But the fuze was always toward the muzzle and away from the blast, a
practice which dated from the early days when mortars were discharged
by "double firing": the gunner lit the fuze of the shell with one hand
and the priming of the mortar with the other. Not until the late
1600's did the method of letting the powder blast ignite the fuze
become general. It was a change that greatly simplified the use of the
arm and, no doubt, caused the mortarman to heave a sigh of relief.
[Illustration: Figure 38--SPANISH 10-INCH BRONZE MORTAR (1759-88).
a--Dolphin, or handle, b--Bore, c--Powder chamber.]
Most mortars were equipped with dolphins, either singly or in pairs,
which were used for lifting the weapon onto its bed. Often there was a
little bracketed cup--a priming pan--under the vent, a handy gadget
that saved spilling a lot of powder at the almost vertical breech. As
with other bronze cannon, mortars were embellished with shields,
scrolls, names, and other decoration.
About 1750, the French mortar had a bore length 1-1/2 diameters of the
shell; in England, the bore was 2 diameters for the smaller calibers
and 3 for the 10- and 13-inchers. The extra length added a great deal
of weight to the English mortars: the 13-inch weighed 25
hundredweight, while the French equivalent weighed only about half
that much. Müller complained that mortar designers slavishly copied
what they saw in other guns. For instance, he said, the reinforce was
unnecessary; it "... overloads the Mortar with a heap of useless
metal, and that in a place where the least strength is required, yet
as if this unnecessary metal was not sufficient, they add a great
projection at the mouth, which serves to no other purpose than to make
the Mortar top-heavy. The mouldings are likewise jumbled together,
without any taste or method, tho' they are taken from architecture."
Field mortars in use during Müller's time included 4.6-, 5.8-, 8-,
10-, and 13-inch "land" mortars and 10- and 13-inch "sea" mortars.
Müller, of course, redesigned them.
[Illustration: Figure 39--COEHORN MORTAR. The British General
Oglethorpe used 20 coehorns in his 1740 bombardment of St. Augustine.
These small mortars were also used extensively during the War Between
the States.]
The small mortars called coehorns (fig. 39) were invented by the famed
Dutch military engineer, Baron van Menno Coehoorn, and used by him in
1673 to the great discomfit of French garrisons. Oglethorpe had many
of them in his 1740 bombardment of St. Augustine when the Spanish,
trying to translate coehorn into their own tongue, called them
_cuernos de vaca_--"cow horns." They continued in use through the U.
S. Civil War, and some of them may still be seen in the battlefield
parks today.
Bombs and carcasses were usual for mortar firing, but stone
projectiles remained in use as late as 1800 for the pedrero class
(fig. 43). Mortar projectiles were quite formidable; even in the
sixteenth century missiles weighing 100 or more pounds were not
uncommon, and the 13-inch mortar of 1860 fired a 200-pound shell. The
larger projectiles had to be whipped up to the muzzle with block and
tackle.
[Illustration: Figure 40--THE "DICTATOR." This huge 13-inch mortar was
used by the Federal artillery in the bombardment of Petersburg, Va.,
1864-65.]
In the last century, the bronze mortars metamorphosed into the great
cast-iron mortars, such as "The Dictator," that mammoth Federal piece
used against Petersburg, Va. Wrought-iron beds with a pair of rollers
were built for them. In spite of their high trajectory, mortars could
range well over a mile, as witness these figures for United States
mortars of the 1860's, firing at 45° elevation:
_Ranges of U. S. Mortars in 1861_
Caliber Projectile Range
weight (pounds) (yards)
8-inch siege 45 1,837
10-inch siege 90 2,100
12-inch seacoast 200 4,625
13-inch seacoast 200 4,325
At the siege of Fort Pulaski in 1862, however, General Gillmore
complained that the mortars were highly inaccurate at mile-long range.
On this point, John Müller would have nodded his head emphatically. A
hundred years before Gillmore's complaint, Müller had argued that a
range of something less than 1,500 yards was ample for mortars or, for
that matter, all guns. "When the ranges are greater," said Müller,
"they are so uncertain, and it is so difficult to judge how far the
shell falls short, or exceeds the distance of the object, that it
serves to no other purpose than to throw away the Powder and shell,
without being able to do any execution."