As we are reasonably led to conclude that the tumuli and cairns were mostly constructed at one time, as monuments, and not gradually completed as they were filled on the death of successive members of a family or tribe, the large chambered cairns must be considered as a separate class from those first described. It is possible that they may have been designed as the catacombs of a whole tribe; though it is difficult to reconcile such an idea with the improvident habits of a rude people, and with the monumental character usually traceable in these structures. We should rather, perhaps, look upon the chambered cairn as the memorial of the victors on some bloody battle-field. On this supposition the Knoc-kill-goill, or hill of the strangers' graves, would indicate the scene where triumphant invaders had paid the last honours to their dead ere they bore off with them the spoils of victory. Such suppositions, however, are altogether apart from the facts with which we have chiefly to deal. The cromlech, which is now almost universally recognised as a sepulchral monument,[77] formed by far the most laborious and costly memorial which the veneration or gratitude of primitive ages dedicated to the honour of their illustrious dead. It consists of three or four large unhewn columns, supporting a huge table or block of stone, and forming together a rectangular chamber, which is frequently further inclosed by smaller stones built into the intervening spaces. Within this area there is generally found the skeleton, disposed in a contracted position, and accompanied with urns and relics of an early period. As the sepulchral tumulus is justly regarded as only a gigantic grave-mound, so the origin of the cromlech may be traced to the desire of providing a cist for the last resting-place of the chief or warrior, equally distinguished from that which sufficed for common dust-- "A little urn--a little dust inside, Which once outbalanced the large earth, albeit, To-day a four-years' child might carry it!"[78]