[Sidenote: Mosaic of the Lateran Palace at Rome.] The first of these is the famous mosaic of the Lateran triclinium, constructed by Pope Leo III about A.D. 800, and an exact copy of which, made by the order of Sextus V, may still be seen over against the façade of St. John Lateran. Originally meant to adorn the state banqueting-hall of the Popes, it is now placed in the open air, in the finest situation in Rome, looking from the brow of a hill across the green ridges of the Campagna to the olive-groves of Tivoli and the glistering crags and snow-capped summits of the Umbrian and Sabine Apennine. It represents in the centre Christ surrounded by the Apostles, whom He is sending forth to preach the Gospel; one hand is extended to bless, the other holds a book with the words 'Pax Vobis.' Below and to the right Christ is depicted again, and this time sitting: on his right hand kneels Pope Sylvester, on his left the Emperor Constantine; to the one he gives the keys of heaven and hell, to the other a banner surmounted by a cross. In the group on the opposite, that is, on the left side of the arch, we see the Apostle Peter seated, before whom in like manner kneel Pope Leo III and Charles the Emperor; the latter wearing, like Constantine, his crown. Peter, himself grasping the keys, gives to Leo the pallium of an archbishop, to Charles the banner of the Christian army. The inscription is, 'Beatus Petrus dona vitam Leoni PP et bictoriam Carulo regi dona;' while round the arch is written, 'Gloria in excelsis Deo, et in terra pax omnibus bonæ voluntatis.' The order and nature of the ideas here symbolized is sufficiently clear. First comes the revelation of the Gospel, and the divine commission to gather all men into its fold. Next, the institution, at the memorable era of Constantine's conversion, of the two powers by which the Christian people is to be respectively taught and governed. Thirdly, we are shewn the permanent Vicar of God, the Apostle who keeps the keys of heaven and hell, re-establishing these same powers on a new and firmer basis[145]. The badge of ecclesiastical supremacy he gives to Leo as the spiritual head of the faithful on earth, the banner of the Church Militant to Charles, who is to maintain her cause against heretics and infidels. [Sidenote: Fresco in S. Maria Novella at Florence.]