this, he commanded a vast trench to be dug, and a huge rampart to be thrown up, as the Roman generals had done centuries before; and this gigantic work he extended for nearly a hundred miles, carrying it over marsh, and morass, and mountain, from the river Dee to the entrance of the Wye, strengthening it also with fortresses, which he manned with chosen and hardy soldiers. But the Welsh were not long before they filled up a large portion of the ditch, made a wide gap through the ramparts, and fell upon Offa's warriors while they were holding their Christmas feast, and more than one Saxon fortress was left standing all throughout that dark winter night without a sentinel. Offa again arose, and revenged the deaths of his followers; the king of North Wales, and many of the old British nobles, fell at the battle of Rhuddlan, and those who were taken prisoners were doomed to the severest slavery. Mercia was not disturbed again by the Welsh during the reign of Offa the Terrible. The remains of the immense work, which ages after retained the name of Claudh Offa, or Offa's Dyke, are still visible, and for centuries were the acknowledged barrier that divided England from Wales; many an unrecorded combat was fought on those ancient boundaries, and the remains of many a hero, whose name will never now be known, lie buried deep down within those filled-up trenches. Perhaps Offa's marriage with Drida was the first cause of his opening a correspondence with the renowned Charlemagne; but whatever it might be, the letters that passed between them reveal the earliest traces of a protected trade with the continent. The Frankish king offered to permit all pilgrims to pass securely through his dominions; and such as came not on religious missions, but were engaged in commerce, were to pass safely to and fro, after paying the requisite duties. To Offa, Charlemagne sent as proofs of his kindness and friendship, a rich belt, an Hungarian sword, and two cloaks of silk. Trifling as these matters may at first appear, they show what silent strides civilization was already making; duties paid on commerce for protection are different things to the dogs and horses which, centuries before, the Britons were wont to present to the Roman emperors whenever they required their aid.