CHAPTER I. THE CHURCHES IN THE WEST. [Sidenote: Early notices of the British Church.] In endeavouring to form a just conception of the history and characteristics of the early Celtic Churches of the British Isles, it is necessary at the very outset to discriminate between three consecutive periods, which are strongly contrasted. The first is that period which preceded the withdrawal of the Roman troops from Britain and the termination of the civil government of the Roman province there in the beginning of the fifth century; the second, the period of isolation which followed, when the invasion of the Roman provinces in Gaul and Britain by the Barbarians interposed a barrier of paganism between the churches of Britain and the Continent, and for the time cut off all communication between them; and the third, that which followed the renewal of that intercourse, when they again came into contact in the end of the sixth century. During the Roman occupation of Britain the Christian religion had unquestionably made its way under their auspices into the island, and the Roman province in Britain was, in this respect, no exception to the other provinces of the empire. It can hardly be doubted that, as early as the second century of their occupation, a Christian Church had been established within its limits, and there were even reports that it had penetrated to regions beyond it. It is unnecessary for the purpose of this work, and it would be out of place here, to enter into any inquiry as to the actual period and history of the introduction of the Christian Church into the British province, a subject which has been fully discussed by other writers.[1] Our more immediate concern is with the churches founded beyond its limits, among those tribes termed by the Roman writers Barbarians, in opposition to the provincial Britons. Suffice it to say that during the Roman occupation the Christian Church in Britain was a part of the Church of the empire. It was more immediately connected with that of Gaul, but it acknowledged Rome as its head, from whom its mission was considered to be derived, and it presented no features of difference from the Roman Church in the other western provinces. [Sidenote: Church of Saint Ninian.]