{15} Where a bishop's throne was erected, it was placed on the south side of the choir, which is ecclesiastically always favoured more than the north. Of the stalls on the south side of a choir the one most to the right is of course the easternmost; and it is here that the ancient thrones remain of the bishops of Exeter, St David's and Durham. Again, even if it was not a cathedral church, there were occasions when it was not convenient for an abbot to be so remote from the altar as the return stalls, _e.g._, at certain portions of the Mass; for such occasions alternative seats were provided for the abbot and prior; the former occupying the easternmost stall on the south side, the prior that on the north. At Peterborough there is evidence that the abbot's seat was on the south, at the east end of the choir, near the _ostium presbyterii_.[5] At Ripon the bishop occupies the easternmost stall in the south side, which from the carving of a mitre at the back appears to have been originally assigned to the Archbishop of York; the place of honour opposite is occupied by the Wakeman or Mayor of the city. * * * * * {16} CHAPTER II POSITION, NUMBER AND ARRANGEMENT OF STALLS The history of the changes of position of the stalls of the clergy is one of the most curious and least understood episodes in ecclesiology; it may be worth while therefore to go into it somewhat at length, and to begin at the beginning. As regards what was at all times the main service in the church, the Mass, there were two conditions which it was desirable to bear in mind in church planning. One was that the celebrant should face to the East; the other that the congregation should face to the East. In the earliest Christian days the latter was most often disregarded. The earliest arrangement, normally, of a Christian church was that the sanctuary, containing the altar, should be to the west, and that the laity should be in the nave occupying the eastern portion of the church. At this time the western portion of the church consisted of a semicircular apse. This apse had a double function. On the chord of it was placed the High altar (in the earliest days it was the only altar); and to the west of it stood the celebrant facing east and facing the congregation, as he does to this day at St Ambrogio, Milan, and other churches which retain this primitive plan. Behind the altar, ranged round the apse, were the seats of the clergy, having in the centre the throne of the bishop. Thus the apse, like the chancel of an English parish church, had a double function; the portion containing the altar was the sanctuary, the portion containing the seats of the bishop and his presbyters was the choir; basilicas so orientated were divided into nave, sanctuary, choir; whereas English parish churches divide into nave, choir, sanctuary. Many examples of basilicas with eastern nave and western choir still survive in Rome, Dalmatia, and Istria. To this day