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.
4. Batteries on a coast—generally consist of only an epaulement, without much attention being paid to the ditch; they are, however, sometimes made with embrazures, like a common gun battery; but the guns are more generally mounted on traversing platforms, and fire over the epaulement. When this is the case, the guns can seldom be placed nearer than 3¹⁄₂ fathoms from each other. The generality of military writers prefer low situations for coast batteries; but M. Gribauvale lays down some rules for the heights of coast batteries, which place them in such security, as to enable them to produce their greatest effect. He says the height of a battery of this kind, above the level of the sea, must depend upon the distance of the principal objects it has to protect or annoy. The shot from a battery to ricochet with effect, should strike the water at an angle of about 4 or 5 degrees at the distance of 200 yards. Therefore the distance of the object must be the radius, and the height of the battery the tangent to this angle of 4 or 5°; which will be, at the above distance of 200 yards, about 14 yards. At this height, he says, a battery may ricochet vessels in perfect security; for their ricochet being only from a height of 4 or 5 yards, can have no effect against the battery. The ground in front of a battery should be cut in steps, the more effectually to destroy the ricochet of the enemy. In case a ship can approach the battery so as to fire musquetry from her tops, a few light pieces placed higher up on the bank, will soon dislodge the men from that position, by a few discharges of case shot. It is also easy to keep vessels at a distance by carcasses, or other fire balls, which they are always in dread of.