2. _Howitzer_ BATTERIES.--The dimensions of howitzer batteries are the same as those for guns, except that the interior openings of the embrazures are 2 feet 6 inches, and the soles of the embrazures have a slope inwards of about 10 degrees. 3. _Mortar_ BATTERIES.--Are also made of the same dimensions as gun batteries, but an exact adherence to those dimensions is not so necessary. They have no embrazures. The mortars are commonly placed 15 feet from each other, and about 12 feet from the epaulement. _Note._--Though it has been generally customary to fix mortars at 45°, and to place them at the distance of 12 feet from the epaulement, yet many advantages would often arise from firing them at lower angles, and which may be done by removing them to a greater distance from the epaulement, but where they would be in equal security. If the mortars were placed at the undermentioned distances from the epaulement, they might be fired at the angles corresponding: At 13 feet distance for firing at 30 degrees. 21 20 30 15 40 10 over an epaulment of 8 feet high. A French author asserts, that all ricochet batteries, whether for howitzers or guns, might be made after this principle, without the inconvenience of embrazures; and the superior slope of the epaulement being inwards instead of outwards, would greatly facilitate this mode of firing. If the situation will admit of the battery being sunk, even as low as the soles of the embrazures, a great deal of labour may be saved. In batteries without embrazures, this method may almost always be adopted; and it becomes in some situations absolutely necessary in order to obtain earth for the epaulement; for when a battery is to be formed on the crest of the glacis, or on the edge of the counterscarp of the ditch, there can be no excavation but in the rear of the battery.