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.
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.