There must be a battery to enfilade every face of the work to be besieged, that can in any way annoy the besiegers in their approaches. These batteries, at least that part of them to be allotted for guns, need not be much longer than the breadth of the rampart to be enfiladed, and will not therefore hold more than 5 or 6 heavy guns; which, with two more to enfilade the opposite branch of the covert way, will give the number of guns for each ricochet battery. As the breaching batteries, from their situation, effectually mask the fire of the first or ricochet batteries, the same artillery generally serves for both. Having thus ascertained the number of heavy guns, the rest of the ordnance will bear the following proportion to them:
Mortars. From 8 inch to 13 inch, about ¹⁄₃.
Small Mortars. About ¹⁄₄.
Heavy Howitzers. About ¹⁄₃.
The fewer kinds of ordnance which compose the demand the better, as a great deal of the confusion may be prevented, which arises from various kinds of ammunition and stores being brought together.
The carriages for the ordnance are generally as follows:
For 24 Prs. ⁵⁄₆ the number of guns.
For Mortars, ⁸⁄₉ the number of mortars.
For Howitzers, ³⁄₄ the number of howitzers.
For Stone Mortars, ⁶⁄₇ the number of mortars.