According to Paul B. du Chaillu, one of the more recent and exhaustive writers on the subject, the Viking age extended from the second to the middle of the twelfth century A.D. For a long time—centuries no doubt—individuals were wont to come as traders, and in that capacity may have been welcomed. But towards the end of the eighth century an alarming development took place. Issuing from the viks or bays of Norway and Denmark, the notorious Vikings appeared as depredators and conquerors. 787 is given as the date when first their hostile vessels were seen in English waters. And henceforward concerted attempts were made to land on our shores and annex our territory. In 793 the work of plunder was effectively inaugurated by an attack on Lindisfarne and other points in Northumbria. The monastery on that island was laid waste, and the Northumbrian kingdom itself so crippled that it lost the commanding influence it wielded in the days of Adamnan and Bede and their friend King Aldfrid. Next year the marauding Norsemen emerged in the Western Isles, which from this time till the middle of the thirteenth century were destined to be favourite haunts and special theatres of their operations. They quickly found and sacked defenceless Iona, and for years took spoils of the sea between that Island and Erin. The Hebrides and the Isle of Man were at their mercy in 798, and still insatiate with former booty, in 802 they revisited Iona and burned its sacred buildings to the ground. Returning four years later, they put the whole community to the sword, numbering no fewer than sixty-eight persons. Iona truly had cause to dread the unceasing attentions of these terrible strangers, for each visit seemed more appalling than the other. Baulked in their efforts to get the silver shrines and relics of the departed Columba, the freebooters made another swift and dire descent upon the island in 825. Trained by sad experience, the monks on this occasion had taken the precaution to bury their treasure-trove in a hole in the earth, covering the surface with sods. And when their fierce assailants burst upon the unprotected sanctuary, they found the holy St. Blathmac, who was probably acting-abbot at the time, standing before the altar. Of him they impetuously demanded the way to the hidden objects of their pursuit—the precious silver shrines—and when he calmly refused, insisting that he did not know the place of concealment which his brethren had selected, they savagely murdered him on the spot. The Annals of Ulster record the martyrdom, and Walafridus Strabo, a contemporary on the Continent, gives an interesting metrical account of the event in Latin, gathered no doubt from one or other of the monks who had fled to him from these islands through terror of the Norse.