Giraldus Cambrensis, when at Rome, saw some manuscript which contained a list of the five provinces of fourth-century Britain--otherwise unknown throughout the Middle Ages (_Archaeol.

Oxoniensis_, 1894, p.

224).] But we are moving in a dim land of doubts and shadows.

He who wanders here, wanders at his peril, for certainties are few, and that which at one moment seems a fact, is only too likely, as the quest advances, to prove a phantom.

It is, too, a borderland, and its explorers need to know something of the regions on both sides of the frontier.