of fortification. The conquest of a fortress with a strong garrison can, therefore, much more readily repay the sacrifice it costs than one with very strong works.
(e) The facility of moving the siege train. Most sieges fail for want of means, and the means are generally wanting from the difficulty attending their transport. Eugene’s siege of Landreci, 1712, and Frederick the Great’s siege of Olmütz, 1758, are very remarkable instances in point.
(f) Lastly, there remains the facility of covering the siege as a point now to be considered.
There are two essentially different ways by which a siege may be covered: by entrenching the besieging force, that is, by a line of circumvallation, and by what is called lines of observation. The first of these methods has gone quite out of fashion, although evidently one important point speaks in its favour, namely, that by this method the force of the assailant does not suffer by division exactly that weakening which is so generally found a great disadvantage at sieges. But we grant there is still a weakening in another way, to a very considerable degree, because—