From the above calculation, Carnot concludes, that no fortified place, whatever be its size, if defended in this way, can he taken by any method of attack presently in use. Nor is the certain destruction of the besieging force the only advantage of this new method. Economy, both in men and money, is another and a powerful recommenda tion in favour of the system. The garrison is neither ex posed to danger, nor harassed by a laborious defence. A few companies of artillerymen arc alone requisite, who can carry on their operations without any danger from the enemy's fire, and without any interruption from dismount ed guns, or broken carriages. The great bulk of the garrison have nothing to do hut watch the most favoura ble moment for making a sortie ; and by thus obliging the besiegers to keep strong guards on their works, they ren der the vertical fire more effective. It has already been shenn what execution may be done by six mortars alone ; and from this it may easily be calculated what any greater number might effect in a given time. It is not necessary that all the mortars should be of the same size, nor that they should be all planted hi the same places. They may be of various calibres, and mounted on different parts of the works, according to the distance of the besiegers. It is obvious, however, that, at a given expense, more exe cution may be done by such mortars, than by artillery of the common sort. As the charge is in general small, per haps cast iron balls might he strong enough to resist the shock, without breaking, which would of course diminish the expellee still more. But even though it were found that these did not answer, bars of iron, which are used for many other purposes during a siege, by being cut into pieces of about an inch in length, might be used instead of balls; and if the garrison were supplied with a great number of large mortars or swivels, even this expellee might be saved by loading them with stones. The num ber of stones discharged from a single mortar at once would not be indeed above one-tenth of the iron balls ; be cause stones, to produce the same effect, must lie so many times larger. But if the number of mortars were ten times greater, the total effect would be the same.
Having stated some of the advantages of his system, Carnot proceeds to chew, that it is only by adopting it that the balance between the modern systems of attack and defence can be turned in favour of the latter. The dura tion of a siege, he observes, scarcely ever extends to six or seven weeks, and, in most cases, does not exceed twenty two or twenty-three days. Of these, fourteen are gene rally occupied in constructing the approaches ; so that the actual attack on the place is reduced to eight or nine days. The cause of this very limited period of defence is to be ascribed, he thinks, partly to the impossibility, in the pre sent system of defence, of mounting artillery, so as not to be very soon silenced, and partly to the want of such a method of firing as can reach the besiegers behind their intrenchments. Both of these desiderata are supplied by Lis method, which he then proceeds to vindicate from some objections that have been started against it. These objec tions arc as follow : 1st, That the balk 'recommended are not large enough to produce the desired effect.
2d, That the besiegers would avoid the fall of the shot, by keeping out of their reach ; and, 3d, That the method recommended would consume a great deal of iron.
In answer to the first objection, lie observes, that there is nothing unreasonable in sup posing that a square piece of iron, of the size of a pigeon's egg, should, in descend ing through 120 feet, acquire velocity sufficient to kill a man. But should this be questioned, he appeals to the
example of the ancients, who with their slings, which car-, :led to a much less distance than modern swivels, and with balls much lighter, easily killed or maimed their enemies.
To the second objection he replies, that it can only be worthy of refutation, when it has been shewn that a be sieging army may take a place without approaching it. And, On the third, lie remarks, that for the very same rea son a garrison should not use artillery of the common kind, because it will consume a great quantity of lead. But the force of the objection is still more completely removed, when it is remembered that stones may be substituted in the place of metal balls.
The ingenious author is not satisfied with replying to objections that have actually been made against his sys tem ;—he also anticipates others that might be advanced. Ile observes in particular, that it would be impossible for the besiegers to approach the place under the protection of blindages, because it would be impossible for them to find either time or materials for the construction of such works ; and even if they could, the slightest sortie from the garrison would throw them into confusion, and destroy in a moment the fruits of their long labour.
But it is not only before a breach has been made that this new system of defence can be employed. It is equally effectual in resisting an assault, provided there be an interior intrenchment between the rampart and the place, when a few mortars have been mourned, and reserved for the moment of the attack. At this moment, the garrison is to retire from the breach, and the mortars of the re trenchment are to open at once with a discharge of balls or stones. The consequence of this must be total destruc tion, or at least immense loss, to the breaching party. Should any of them in the mean time gain a footing on the rampart, they must be in great confusion, and may therefore be easily dislodged with the bayonet, the garri son taking care to attack them the moment the fire ceases.
Such is a short outline of the system of defence propos ed by one who appears to have devoted the efforts of a powerful mind, and the labours of a long life, to the im provement of a science interesting above all others to his country, but which military men, in general, have been too ready to regard as incapable of farther improvement. In comparing this system with what is still commonly practised, it is impossible to avoid being struck with the radical difference in the principles on which they are founded. In the old method, the garrison acts almost solely on the defensive ; it waits the advance of the be siegers, and is obliged to sustain the heaviest shock after half its means of defence have been destroyed ; but in Car not's method, the garrison, by a combination of sortees and vertical fires, is constantly acting on the offensive. By the one it cuts off weak parties, and destroys their works, and by the other it assails the strongest force with a certainty of success unknown to every other species of artillery. In a word, it puts into the power of the defen ders all the advantages that have been for so long a time exclusively possessed by the besiegers, both in offensive and defensive operations.