It is highly improbable that any large number of the Roman towns perished during the harassing period within which the Pictish invasions fall, at all events by violent means. The marauding forays of such barbarians are not accompanied with battering trains or supported by the skilful combinations of an experienced commissariat: wandering banditti have neither the means to destroy such masonry as the Romans erected, the time to execute, nor in general the motive to form such plans of subversion. One or two cities may possibly have fallen under the furious storm of the Saxons, and Anderida is recorded to have done so: more than this seems to me unlikely: Keltic populations have generally been found capable of making a very good defence behind walls, in spite of the ridiculous accounts which Gildas gives of their ineffectual resistance to the Picts[785]. The Roman cities perished, it is true, but by a far slower and surer process than that of violent disruption; they crumbled away under the hand of time, the ruinous consequences of neglect, and the operation of natural causes, which science finds no difficulty in assigning. We may believe that the gradual impoverishment of the land had driven the population to crowd into cities, even before the retreat of the legions; and that the troublous era of the tyrants[786] completely emptied the country into the towns. But even if we suppose that citizens remained and, what is rather an extravagant supposition, that they remained undisturbed in their old seats, we shall find that there are obvious reasons why they could not maintain themselves therein. There are conditions necessary to the very existence of towns, and without which it is impossible that they should continue to endure. They must have town-lands, and they must have manufactures and trade: in other words they must either grow bread or buy it: but to this end they must have the means of safe and ready communication with country districts, or with other towns which have this. It matters not whether that communication be by the sea, as in the case of Tyre and Carthage[787]; over the desert, as at Bagdad and Aleppo; down the river or canal, along the turnpike road, or yet more compendious railway: easy and safe communication is the condition _sine qua non_, of urban existence. ----- Footnote 785: According to him, the Britons suffered the Picts to pull them off the wall with long-hooks. “Statuitur ad haec in edito arcis acies, segnis ad pugnam, inhabilis ad fugam, trementibus praecordiis inepta, quae diebus ac noctibus stupido sedili marcebat. Interea non cessant uncinata nudorum tela, quibus miserrimi cives de muris tracti solo allidebantur.” Gild. xix. Beda copies this statement almost verbatim. Hist. Eccl. i. 12. Footnote 786: