If every thing has been prepared, and the enemy's engi neers should make their appearance, they are to be receiv ed with a discharge of grape-shot or balls. This only, however, in case of their approaching in parties, as this sort of ammunition is never to be wasted on a single man. Small calibres are generally used for this purpose, to pre vent the besieger from becoming acquainted with the range of the ordnance. That the engineers may not approach during the night, small posts are placed before the covered way. The commandant also takes care to keep up a coat munication with the army, or the neighbouring fortresses, that, if succours arrive, they may be able to enter with fa cility, Should any parts of the enemy's camp lie within reach of the lire of the garrison, it is to be cannonaded as soon as finished, but not sooner. To prevent the enemy from getting acquainted with the weakest side of the for tress, a great smoke may be made, by burning straw, or firing smoke•balls of various kinds, so as to conceal seve ral fronts. Sometimes also false drawings, or similar de vices, may serve to give the enemy an erroneous idea of the strength of different fronts.
The side which the enemy is determined to attack, may be known from the situation of his depots of materials, and from seeing the engineers constantly at work. This front, in particular, is to be put into a proper state of defence, the country before it being illuminated during the night by fire balls, and outposts must be placed before the covered way. Small works are here also useful, in making the besieger begin his first parallel, as well as all his others, at a great distance. When it is necessary to leave these works, to prevent the enemy deriving any advantage from them, their parapets are to be sprung and destroyed by small mines.
When it has been discovered, by means of spies or light balls, when and where the enemy opens his trenches, a constant fire must. be kept up, in order to disperse the workmen. Next morning the engineers are to survey the enemy's work, and a fire opened on such parts of them as can be enfiladed. In the beginning of the siege, a strong fire ought to be kept up, to hinder the enemy from com pleting his works ; but afterwards it is directed only to those places where it may be of the greatest use, particu larly where the enemy has to construct his batteries.
Should the enemy's batteries be finished, the guns arc rather to be withdrawn than destroyed ; but if one of the enemy's batteries can be dismounted, all the force is at first directed against one merlon, and then against the others successively.
Such parts of the for tress as have been damaged must be repaired during the night, that they may be in a proper state for service the following morning.
Should the enemy's parallel come so close to the cover ed way, that the fire of small arms can reach it, riflemen should be placed there, to fire at every one who may ap proach the trenches, particularly when the engineers or officers appear. The fire of the riflemen should also be directed against the head of the trenches, or where they are not quite finished, as also where batteries are to be erected.
For the same purpose also, small pieces of ordnance, and in particular small mortars, placed in the saliant angles of the covered way, may be used with the greatest advan tage. Counter approaches are sometimes used ; but cer tainly they are of no benefit, it being ridiculous to suppose that a garrison can, with any advantage, besiege the army by which it is itself besieged.
Another means of defence against a siege, are sorties or sallies, for the purpose of procuring provisions, opening a communication with the army, or attacking some part of the enemy's works. They are undertaken sometimes be fore, and sometimes after the place has been invested ; and they differ in the strength of the parties employed, accord ing to the object in view.
Sorties against the enemy at some distance from the for tress, are sometimes liable to be cut• off, and therefore only to be undertaken when the retreat can be secured. As such sorties also generally cost a great many men, they should only be undertaken when there is a fair prospect of obtaining some particular advantages, and where the gar rison is so strong that a sufficient number will remain to defend the fortress properly.
Sorties which require a strong force, should never be undertaken unless they have a particular object in view, and then they are to be made by a sufficient number of troops to execute it without difficulty. Particular circum stances sometimes determine a garrison to make a strong sortie ; but it is never in this case to be clone if the men could afterwards be of greater service in the defence of the fortress. What relates to the execution of these sorties, the nature of the ground, and the different movements, will be farther illustrated under other articles.
Small sorties are generally made by parties of about 20 to 30 men, who secretly leave the covered way, and attack suddenly with great noise. They then destroy every thing belonging to the trenches, or set fire to them, spike up the enemy's guns, overldad them, Ste. for all which purposes they arc provided with the necessary assistance of work men, tools, and materials, taking care always to retreat as soon as the enemy's reinforcements arrive. These little attacks are particularly useful after a mine has been sprung, before the garrison of the trenches has recovered from its fright, and order restored.