When the wave of the Norman invasion first rolled across St. George's Channel, the success was as easy and appeared as complete as William's conquest of the Saxons. There was no unity of purpose among the Irish chieftains, no national spirit which could support a sustained resistance. The country was open and undefended,[279] and after a few feeble struggles the contest ceased. Ireland is a basin, the centre a fertile undulating plain, the edges a fringe of mountains that form an almost unbroken coast line. Into these highlands the Irish tribes were driven, where they were allowed to retain a partial independence, under condition of paying tribute; the Norman immigrants dividing among themselves the inheritance of the dispossessed inhabitants.[280] Strongbow and his companions became the feudal sovereigns of the island, holding their estates under the English crown. The common law of England was introduced; the king's writ passed current from the Giant's Causeway to Cape Clear;[281] and if the leading Norman families had remained on the estates which they had conquered, or if those who did remain had retained the character which they brought with them, the entire country would, in all likelihood, have settled down obediently, and at length willingly, under a rule which it would have been without power to resist. [Sidenote: Two causes of the decline of their authority.] [Sidenote: Absenteeism.] An expectation so natural was defeated by two causes, alike unforeseen and perplexing. The Northern nations, when they overran the Roman Empire, were in search of homes; and they subdued only to colonize. The feudal system bound the noble to the lands which he possessed; and a theory of ownership of estates, as consisting merely in the receipt of rents from other occupants, was alike unheard of in fact, and repugnant to the principles of feudal society. To Ireland belongs, among its other misfortunes, the credit of having first given birth to absentees. The descendants of the first invaders preferred to regard their inheritance, not as a theatre of duty on which they were to reside, but as a possession which they might farm for their individual advantage. They managed their properties by agents, as sources of revenue, leasing them even among the Irish themselves; and the tenantry, deprived of the supporting presence of their lords, and governed only in a merely mercenary spirit, transferred back their allegiance to the exiled chiefs of the old race.[282] This was one grave cause of the English failure, but serious as it was, it would not have sufficed alone to explain the full extent of the evil. Some most powerful families rooted themselves in the soil, and never forsook it; the Geraldines, of Munster and Kildare; the Butlers, of Kilkenny; the De Burghs, the Birminghams, the De Courcies, and many others. If these had been united among themselves, or had retained their allegiance to England, their influence could not