certain places, and there is no doubt a pious hope that the hostile cruiser bent on destroying a mercantile port defended by a few six-inch guns will be sufficiently obliging to fire at the fort instead of at the docks and shipping that it 'protects.' The cardinal and obvious axiom that the enemy will not come unless in force calculated to make the defence of no account is invariably ignored altogether. Our forefathers put up martello towers, and the enemy, for lack of anything better to do, used now and again to attack them. On these classical grounds we have erected the martello towers of our own age.
Now, bearing in mind the axiom that the attack will only be delivered in force sufficient to overcome all opposition—unless we presuppose the enemy insane he will attack under no other conditions—it would seem essential to have all fortifications of the very strong order, and at least able to defy anything except perhaps a very considerable battle fleet. In theory, perhaps, such a principle is accepted: in practice the prohibitive expense is in the way. It would cost altogether too much.
A recognition of this fact, coupled with the idea of being able to use the defence elsewhere as offence is undoubtedly the origin of 'coast-defence battleships.' These in the original idea of them were to be scattered around the different harbours to take the place of forts, while, the need for such defence being past, they could be used for various offensive purposes as ships.
